Color plays an important role in the design of visual displays. In visual displays, color is used in letters, signs, and figures, which are the basic components of visual information, and color itself can also convey emotions and impressions. In this way, color is used as a means of communicating information. However, it is known that there is a diversity of color vision, and not all people see the same colors. This means that senders must consider their recipients’ color vision characteristics when designing color. For example, people with dichromatic color vision (so-called “color vision deficiencies”) have color combinations between which they cannot distinguish, called confusion colors ― the ability to distinguish between colors is called an issue for Class A Observation and can be measured objectively ―, and their color vision may differ from that of people with trichromatic color vision (called “normal” color vision)^.

Because color perception is a personal and subjective experience, each individual knows only his or her own color perception and cannot know exactly what colors others see ― determining how a color appears is an issue for Class B Observation and cannot be objectively measured. This is particularly true between people with trichromatic and dichromatic color vision (trichromats and dichromats, respectively). At the very least, color barrier-free design and color universal design aim to ensure the transmission of information through color while avoiding confusion colors. To put this color universal design into practice, it is essential to know various color vision characteristics and forms of color perception, and many studies have revealed the confusion colors of dichromats and have also inferred the colors that dichromats are likely to see Brettel et al., 1997). Currently, color universal design methods are being proposed and widely used based on these insights into dichromatic vision.

There are two main methods of color universal design methods. One is to simulate what colors dichromats see and to evaluate color design based on the simulation results (commonly called dichromatic vision simulation). The simulation is based on the results of hue matching experiments^{(Graham and Hsia, 1958)}conducted on people with different color vision characteristics in their left and right eyes, whereby one eye has trichromatic vision and the other eye has dichromatic vision. The main evaluation criteria here are whether there is confusion color in the scheme and whether the information defined by the colors is clearly conveyed. If there are any confusion colors or difficulties in distinguishing the colors used, the color scheme should be reconsidered.

Color universal design based on dichromatic vision simulation and verification can be easily implemented by using goggle-type color weakness simulation filters with functional filters as hardware and smartphone applications, graphic design software, and photo retouching applications as software. However, the accuracy of this dichromatic vision simulation remains controversial (Broackes, 2010; Sunaga et al., 2013).

Another method is to create a color palette that is known in advance not to contain confusion colors and then select the colors to be used in the color scheme from that palette. The Color Universal Design Recommended Color Palette is a proposed representative example of such a color palette Color Universal Design Recommended Color Palette Production Committee, 2018). The latest guidebook for the recommended color scheme set (2nd edition) includes examples of recommended color schemes for different applications, such as painting, printing, and screen use, and provides easy-to-understand explanations. The book is recommended for those who are new to color universal design because it includes an explanation of color universal design.

In addition to the above two methods, a new third method has been proposed to devise color designs on the basis of color schemes for people with dichromatic vision Sato et al., 2010; Sunaga et al., 2018). The characteristic of this method is that it comprises two stages: first, color schemes for dichromats and second, color schemes for trichromats. In the color scheme for dichromats, colors are selected from the color set that can be distinguished by dichromats, so dichromats will always be able to recognize the color scheme. The next step is to change the color scheme to one that is suitable for people with trichromatic vision. Because the second color scheme is limited to colors on or near the confusion color line of the colors selected for the scheme for dichromats, both the colors before and after the change will be confusion colors or will appear to be very similar to dichromats. In other words, even if a dichromat observes a color scheme for trichromats, he or she will observe a color scheme that appears almost identical to the one used for dichromats.

In addition to the three methods described above, there are also algorithms for automatically detecting confusion colors and transforming them, methods for using fuzzy constraint satisfaction problem solving to determine color schemes suitable for people with different color vision characteristics, and supplementary lighting designs that make it easier to see color differences.

(Shoji Sunaga)

Related Classes

Media Design Course Color Science

Media Design Course Media Science Seminar II

References

• Brettel, H., F. Viénot, J. D. Mollon (1997), “Computerized Simulation of Color Appearance for Dichromats,” Journal of Optical Society of America A, 14-10, 2647-2655.
• Broackes, J. (2010) “Unilateral Colour Vision Defects and the Dimensions of Dichromat Experience,” Ophthalmic and. Physiological Optics, 30-5, 672-684.
• Graham, C. H., Hsia Yun (1958) “Color Defect and Color Theory,” Science, 127-3300, 675-682.
• Sunaga, Shoji, Tomomi Ogura, Takeharu Seno (2013) “Evaluation of a Dichromatic Color-Appearance Simulation by a Visual Search Task,” Optical Review, 20-2, 83-93, 2013.
• 太田安雄、清水金郎（1999）『色覚と色覚異 これだけは知っておきたい理論と実際』金原出版
• カラーユニバーサルデザイン推奨配色セット制作委員会編（伊藤啓、社団法人日本塗料工業会、DIC 株式会社、特定非営利活動法人カラーユニバーサルデザイン機構，前川満良）（2018）『カラーユニバーサルデザイン推奨配色セット ガイドブック 第２版』
• 佐藤尊之、東洋インキ製造株式会社 (2010-07021)「色を選択する方法」特許第4507641号
• 須長正治、城戸今日子、桂重仁（2018）「系統色名カテゴリを用いた２色覚基点のカラーユニバーサルデザイン配色法の提案」『日本色彩学会誌』42巻5号、209-217頁