The use of colour to help visualize information

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THE USE OF COLOUR TO HELP VISUALIZE INFORMATION? HANS JORGEN EHLERS Ernst Klctt Verlag. Stutq[an. FRG Abstract--The prcsentaUonattempts to show how ceded display attributes, especiallycolour, can help to make business and presentation graphics to communicate better. Essentialsof the instructional functions of colour and some of the consmunts are outlined. The second Imrt covers colour m the CEPT European Vidcotex rccommendauon and how the Stowing acceptance of microcomputers will promote colour computers. i. DISPLAY ENHANCEMENTS For centuries, educational publishers have used colour to help visualize informauon. Colour not only enhances illustrations, helps to distinguish and differenuate structures, but also increases the amount of information that can be presented at one time. Colour is also widely used to help give a better understanding of the graphic organization of text; intelligent application of colour is an aid to locating particular information and facilitates the display of structure in a given unit. My company, Ernst Klett Publishers and Printers in Stuttgart, regards itself as a pioneer in the use of coiour and true-to-life pictorial information in education and instruction. A lot of what we, as still dominantly paper-medium printers and publishers, have learned, can also be used advantageously in computer-aided decision support systems and business computer graphics. Business and presentation graphics, as typography and spatial layout, belong to the category of display enhancements. They are all tools to facilitate understanding, as the value of information is directly proportional to ease of comprehension. We cannot cover all display enhancements but will concentrate on colour, which has become, in computer graphics and in on-line surroundings, an indispensable added-value technology. W e live in a world of colour. All display enhancements are only saleable if they correspond to user expectancy. Very soon a high percentage of business graphics users are likely to expect colour to make information transfer easier. This preference for colour or even for all kinds of graphically displayed information, as we often hear it from the user community, should not be misinterpreted as a need for presentation graphics or colour per re, but it often expresses an unreflected dissatisfaction with the efficiency of today's information transfer. During my professional life, coiour film, black and white television, high quality inexpensive colour magazines, have been introduced. Soon colour TV can be expected in all households. We live in a world of colour. In our perceptions of what we see, colour ? Prepared for CAMP '83 (Berlin, March 14-17, 1983).

plays an important role. This property of light has a direct effect on our senses, and--more than expected--on our emotions. Today we are used to seeing colour everywhere. So u is understandable to look for equivalents of colour applicauons outsmde one's h o m e also, as all commumcation mcdma influence each other. Most of us expect that all that we are used to, and find acceptable, in one medium should be offered in other media, too. So educational books of the 19505 had to drop line drawings and replace them by halftones. Vet3' soon. black and white illustrations were no longer acceptable, and the textbooks had to have four-colour illustrations in a quality we find in magazines like the "Bunte" (The Coloured) in German-spoakmg countries or the "National Geographic M=~a,tne" in the USA. For centuries, newspapers were in bLackpnnt only: now the reader expects at least colour supplements and coiour illustrations, even if the quality is not yet up to the magazine standard, l am convinced the development of business graphics systems will not be different.

2. COLOUR rSYCHOLOGY Colour is essentially the result of rcacuons of the eyes to the spectrum of light waves, but our attitude to colour is not only based on physics and physiology. Considering the success of books on colour psychology by such authors as Birren or even more so the Swlss Dr. M a x Liischer, one m a y almost take for granted that today's audience knows about the essentials of the subject. But the reactions to colour are not equal in all the countries of the world, due to our environmental conditioning to important aspects of coiour psychology. Black does not everywhere denote mourning or white cleanliness and virginity. Our emotional attitude towards coiour is weft exv~ in language, especially in idiomatic and colloquial exprcs~ons. We 'see red" ('sehen rot," 'voyons rouge') when we are angry, we celebrate "redletter days.' have 'red herrings" of politicians to deal with, and regret the growing number of firms that are 'in the red.' Yellow is a hue that is very often disliked. The old paintings always depict Judas with a yellow coat. 'Yellow journalism' or the 'yellow fever' denote neg-

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ative issues. However, according to Lfischer. yellow is the brightest, most radiant, chromatic coiour. Yellow causes expansion and change, cheerfulness, and high spines are associated to this ambivalent colour. Green is often associated with the inexperienced. We have the 'Gr0nschnabel" in German or the "greenhorns" m American English. The "Greens" are still the most rigorous new political movement in Germany. There are also many expressions where blue is used. mostly in association v~th soberness and gloom. We 'feel blue," listen to 'blue music' and hope that 'blue stockings" do not visit 'blue movies." Orange has become a fashionable colour lately. It is interesting that neither m English. French. or German do we have coilocauons with orange. This mixture of yellow and red ranks high in attentiongetting, where men place it even above red, which is preferred by women. In this scale of attention-getting. blue follows red, then black, green, yellow, violet, and grey. But in a list of the colours liked most, yellow and orange are not in the first positions. Here blue is clearly in front, then red, green, violet, brown, orange, pmk, turquoise, and grey. Children prefer red and purple (a blend of red and blue). Nowadays there are a lot of colour schemes which we are so accustomed to that we react to them almost instinctively. A red sign denotes, worldwide, "stop.' a green button would be used for "start.' Yellow means attentaon. In our warehouse we use colour to associate unit amounts: l0 books are placed in brown paper. 5 in white. This overview of colour psychology could be continued much longer, and our remarks were only intended to show three important issues: • Colour is relative in our perception of it: • The human reactions to colour cannot be standardized. Depending on age, sex, or place, the subjective reactions to colour are different: • Everywhere we find user expectancy to coiours and their meaning. These existing and accustomed colour codes must be considered before designing new applications. But we should not only take coiour psychology into account when we want to use colour. Colour is complex, falling also under the domain of many disciplines: Physics, physiology, chemistry, and even an. The varied characters of coiour provide a new dimension to visual images or compositions. In black and white, compositions can only be made by the spatial arrangement of elements, visual cues of shape, structure orientation and grey value. By adding coiour another dimension is opened up, the capability of the visual composition is increased logarithmically. 3. PERCEPTUAL BEHAVIOUR OF COI,OUR

In order to utilize colour enhancements effectively in business graphics, we have to examine the perceptual behaviour of colour. Time does not allow us to cover extensively here the three basic colour charac-

•tenstics, already established by Helmholtz. and later Ostwald of Leipzig University, before the First World War. They are: • Hue (distinctive shade that differentiates it from other hues): • Value (or tone), lightness or darkness o f a colour

in relation to black or white. Value attributes are the luminosity of a colour, its brilliance or dullness: and • Chroma. the strength or weakness of a coiour (saturation or dilution).

3.1 Colour generation When we want to use coiour as display enhancement. we have to take into account the vaned output medm. be it a TV set or a hardcopy output. CRT devices use electronic beams, whereas pnnters work with colouring pigments that are the basis of the various inks used. There is a considerable difference between colour generation on a CRT device and mixing pigments as we are used to in pnnting, or less easily with a pen plotter or ink-jet printer. Here we use subtractive coiour devices, the overlay of coiours add up to black (absence of colour). In a colour TV, or CRT monitor, we use the additive eolour process. The combination here produces white. The three primary coloursmred, blue. and green--are produced on a CRT terminal by a separate electronic gun for each primary. The complementary colours are obtained by mixing two of these primaries. The consequence of this method of colour generation is easy to understand. White, needing three beams, will be less sharp than yellow, the latter less exact than green. Coloured rims at the character edges can be seen at close view. So one should avoid using complementary colours side by side. Outlining bars or pie charts in a light colour helps. We all know that certain colours generate two-, often almost three-dimensional effects. Colours interact with each other and are perceived dynamically. The accommodation ability of the human eye is only correct in white daylight. For the other colours this accommodation is wrong. This effect, called chromatic aberration, must be considered in adjacent coiour mixing. So if one looks at the colour display, the red parts will appear closer than the blue. These effects can be used to give graphics a three-dimensional character. Receding colours (blue and green) are best used for background information, supporting data, e.g. axes. to be played down. As we all know by comparing black and white, we have different sensitivity to the visible wavelength of light. When the relative luminance of white is 100%, yellow gets down to 90%, cyan (often also called turquoise on CRT output devices) to 70%, green 60%, magenta 40%, red 30%, and blue just above 10%. Technologically it would not be too difficult to include in CRT devices compensation circuitry which could artificially increase the luminance of apparently dim colours like red and blue to an equal level of

The use of coiour to help v~nali~e informauon

brightness. But this eliminates monochrome compatibility and would make it difficult for users with anomalies of colour vision. 3.2 Co/our v:swn deficiency Colour vision deficiency is fairly common to humanity, but not evenly spread among men and women (all ladies present should be able to see R0 or 51 in the tables} as only I% of females have anomalous coiour vision, whereas 8% of males are red/green or rather rarely, blue/yellow blind. Considenng the increasing use of colour to transfer information, we must take into account that at least one out of twenty is weak in perceiving colour differences. Persons with colour vision anomalies have an increased sensativity to luminescence and to variations in colour tone. In colour coding one should therefore avoid one-element-only coding. If possible, muitidimensxonal codingDan expression I like better than redundant colour coding--should be used. We'd better keep the example of the old trat~c light in mind where colour and position give the necessary information. One should also avoid small transient fields at low bnghmess: The smallest area displayed should be at least 1.5 mm to avoid colour diffusion. A presentation in under 3 seconds won't get the necessary attention. Large, bright-coloured fields which can be perceived with plenty of time are better suited. Legibility research has long ago established the most acceptable colour combinations: Black and white; red or blue and yellow; green and red or pink; yellow and blue. Less legible combinations like black on purple, or orange or yellow on white, should be avoided. 4. COMMUNICATION FUNCTIONSOF COLOUR Let us now look at the communication functions of colour. There are many ways to indicate information structure for the user. We have covered typographic and spatial coding elsewhere. In the last decade, colour has become a very important tool to make information transfer easier. Colour graphic cues are indispensable today, especlally wlth the traditional paper media. We must also realize that colour has been used more or less decoratively for a long time. Coloured initials or lines in the early European texts are well-known examples. Though colour can help to make understanding easier, we have to realize that text and graphics that are incomprehensible in black and white won't get their points across any better if they are loudly coioured. Colour should always be used with a clearly defined purpose, e.g., to cut down the glare when a transparency is used with only a short message and a lot of white background. In business lm~sentation graphics, three functions of colour usage are most widely found: Highlighting~ Relating--Discriminating. To empbaciT¢ words or blocks of text.by an attention-getting attribute is an old technique. For highlighting we may use bigger size characters, un-

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deriining, bold face. or other methods of typographical differentiation. Special cuing, e.g., leaving a wide space around a headline, can be used on all kinds of displays, while blinking is only possible with a CRT. A most widely found fo.rm of using colour for highlighting or downplaying is a change of background colour. Vanauons there are more effective than just changing the hue of the characxers. Key p a ~ g e s will be pnnted on a field with a differently coloured background. I can remember well how enth-¢iJsucally this currently-used method was welcomed for instructional material m the early 1950s. Highlighting. when used for graphics--but not for text. is especlally effective when a very. brilliant colour is used. whereas the t~st is lef in red or blue. For information transfer, we often need text or tables of figures or charts that display material which is somehow related. This belonging together can be emphasized by using the same colour, expressing relationship. It is also possible to communicate similarities by using resembling colours; red and pink, or brown and orange, would be good examples. By the use of graphic toning techniques---differem shading patterns---similarities can also be visualized. Colour coding of quantities we have mentioned before. To this "relating" function belongs also the identification of recurring themes by displaying them in the same colour. This method has often been used with educational material by either using tinted paper for different pans of a book, or coloured margins. What has been said above about grouping together is also relevant when we want to discriminate items with different functions. An example from a KJett schoolbook on physics shows a line drawing of a motor. Here the coiours illustrate the pnnciples of a direct current motor. The colour coding of the London Underground map is another example. The new cockpit of the Airbus A310 is able to display a multicoloured map and other display graphics for the pilots wRh a speoal monitor, in both applications colour is used to add clarity and immediacy. Complex data are simplified by colour contrast. We already mentloned some important constraints to be considered when using colour. Foremost. we must have enough contrast between text and background. The level of contrast should always be at least over 65% for good legibility. Colour coding also loses its value under poor lighting conditions. Colour terminals cannot be used in glaring sunlight. A colour printout read under a sodium street light might convey wrong attributes. A very common mistake in the use of coiour, especially by those who are new in the field, is a too arbitrary application at every opportunity. To use more than three, or at most five, colours, including white, is confusing, it is hindering communication instead of helping it. The left side of the b r a i n - responsible for analysis and logic--looks for a reason in coiour attributes. We are so used to decoding the display, we look for cues and get tired and frustrated when we cannot understand the meaningDa lime-

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green sea instead of the blue we are used to. As Prof. Chute points out in a very useful *Analysis of the Instructional Functions of Color and Monochrome Cuing in Media Presentation" low aptitude learners not only get frustrated due to-not being able to understand the cuing, but become overloaded w~th visual input. This is the reason why educational publishers and other providers of instructional material had to learn never to mix decorative use of colour with planned colour cuing. 5. C O L O U R AS A VIDEOTEN A T T R I B U T E

In this presentation i can only deal briefly with colour as an essential Videotex attribute, especmlly in the new CEPT standard. A definiuon of Videotex-without 't" at the end--might be useful. It is a generic name for text communication systems that can also present graphic information. These systems are based on the telephone network and the television screen as output devices. Biidschirmtext. Prestel, Teletel, and Teledata are well-known examples of Videotex systems, each relying on the TV raster standards of different countries. To improve the graphic quality and to augment the so-far limited character set, the relevant European standardizing bodies CCITT (Comitd Consultatif International Tc'.'i/.'graphtqueet T~16phonique) and CEPT (European Conference of Post and Telecommunication) have agreed on a Recommendation which includes all the European systems. This Videotex Presentation Layer Protocol increases the number of characters that can be displayed and also defines colour as an important attribute in all Videotex systems. The early Videotex systems were designed with a wide audience in mind. In most countries TV sets with colour display were available and in daily use, TV typical attributes (coiour, space, flashing) had to be used as the early Viewdata systems had only very limited typographic flexibility and a low resolution (Legotypography). Colour was used to make up for this deficiency. Tests showed the success of this policy. The new standard introduced in Germany last year allows much more typographic and spatial coding for information structuring. Now it is generally possible to stretch characters to twice their height or width. The new Draft Standard also allows double size. But colour still remains the most important attribute. It will be possible to extend the 7 colour range we have now o.n Prestel or Bildschirmtext to various colour palettes of 8 hues each. At a given instant, only one palette may be in use. This extension facility is especially important for firms wanting to display their house colour as exactly as possible. Professional colour usage for presentation graphics, as we have already with some Videotex systems, will also undoubtedly foster coiour graphics applications for hardcopy output.

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6. COl..OUR C O M P U T I N G

The other, even stronger promoter of coioured business graphics is the "mighty micro." From the very. beginning, the ability to handle colour graphics was an important quality enhancement of the personal computer. The microcomputer market growth is legend. Colour helps in this success. We see it in the logo of Apple, but also in new models like the inexpensive Radio Shack's 'Color Computer." From the hardware point of view. the additional price of colour is often only a marketing exercise. but there is still a lack of suitable coloured business graphics software for the micro. Due to the low resolution (pixels on the screen) the graphic capability of microcomputers is nothing to rave about: as happened with Videotex. coiour had to be used to get an acceptable attractive presentation dtspla~ With the new 16-bit microcomputer generation we can expect also a new generation of integrated software offerings that allow text, data and graphics to be swapped between one application program and the next. Presentation graphics can be used with word processing applications to produce a business report with text. tables, and charts in colour. It is hoped that most of the material needed for the so-called "peer-groups' within the company may be produced on microcomputers, whereas the mini and highresolution output devices are intended for outside presentation. Special display generators can also be attached to personal computers, bringing the price for a slide down to $5. In the growing field of microcomputers in schools, the graphic capabilities also play an important part. Whereas COMPUTER-AIDED LEARNING could, for a decade, only rely on a relatively clumsily displayed verbal text with inadequate character sets. graphics and colour have opened a new, highly important field of applications. Computer-aided colour slide generators are able to prepare build-up transparencies where sequences of complex data are broken down into less densely packed slides. In education and training. AV material is widely used. In many countries we may already take for granted that a high percentage of school-leaving pupils have been accustomed to deal with structured textual and graphic material in colour. This will also strongly influence users expectancy. The graphic capability of video-games---another success story world-wide--will also help. 7. S U M M A R Y

Colour graphics are here to stay. There are already discussions on how presentauon graphics could be standardized, and colour also is felt to be an area npe for standardization. Not only in CAD or CAM, but in all apphcations where business information and statistical data have to be presented for fast understanding and decision making. Flexible and easy to use software, together with the increasing intelligence of local computer power today, allows

The use of colour to help visualizeinformauon one to condense code and visualize large amounts of data to make them readable and comprehensible. Already there is a boom for so-called "decision support systems." They allow the user to obtain selective information from a vmnety of databases. It is a highly selective electronic information display for senior management with no special computer training. More and more, the argument is accepted that the advantase of using well-designed coiour graphics is based on the notion that imagery corresponding to daily life is easier to understand. Pictures are better remembered than just words, they help ensure the retention of information. Coloured graphics can stimulate recall of previous knowledge, so essential for comprehension of new material. Coiour plays a vital role in creating visual dynamics, so important for the comprehension of the visual image. Colour is a welcome and asked-for extension to the output of business computing, instructional material preparation, full text, and statistical database retrieval. Coiour instructs and motivates, and speeds identification, resulting in less errors of interpretation. Colour can improve user response-time by 50% by its attentiongetting power and visualizes complex relations, structures, and quantities. Some reasons for this fas~ assimilation of coloured graphics are often quoted. We can comprehend by heanng 150-300 words per minute. We can read. depending on the language used, between 600 and 1200 words per minute. Our eyes have 126 million retinal rods to receive visual stimuli, 5 million colour sensitive cones provide sensitivity to individual wavelengths. The human eye can differentiate approximately 160 colour mixtures, but only thirteen (40 according to other sources) levels of grey. Our visual channel is supposed to be handling 48 million words per minute. Graphics are able to translate masses of data to spatial information which can be processed and seem to result in the information of a "Gestalt," allowing data to be analyzed, not sequentially, but in patterns of parallel, associative fashions. First-class videographics, which we see more and more on our "IV sets, will also increase our expectancy of coiour usage. Everyone active in publishing, be it traditional or electronic, has to accept that text graphics and colour are integrated components, all intended for an optimal transfer of relevant mformarion. Electronic publishing and on-line retrieval services are very likely to enhance what they have to offer by an increasing use of coiour and other pictorial information. REFERENCES Faher l ~ ' n , Color Psychology and Color Therapy. A Factual Study of the Influence of Color on Human Life. McGrawHill, New York, (1950). Hildegrad Bmch-BiUing. Di~nosuscher Biick hinter das Auge. Neue Ziircher Zeuung. p. 35. 8. September 1982. Philip J. Brody, AffecUn$ instmcuonal textbooks through pictures. In The Technology of Text. (Edited by David H. CJ~ 9:2"G

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