Color-blindness, also known as color vision deficiency, means inability or difficulty to see colors. The prevalence of color-blindness in Japanese population is about 4.5% of men and 0.2% of women. That is, at least one in every 20 students have color-blindness in the classroom. There are two kinds of color-blindness depending on the cause of defective color vision: congenital and acquired color-blindness. Since acquired condition is rare, the condition of color-blindness that is usually referred to as inborn anomaly. Congenital color-blindness includes three types. The most common type is deuteranopia, known as defective green vision, that consist of almost 70% of congenital color-blind condition. Protanopia, known as red defective vision, is the second common type, which is almost 30% of congenital color blind condition. Lastly, tritanopia is decreased sensitivity to blue and consists of only 1% or less. The condition of color-blindness used to be referred as sikimou（色盲）in Japanese, but this was misleading and did not respect the fact that the most typical symptom of color-blindness is decreased ability to see certain colors the way most people do.

[Useful websites]

1. Color Vision Navigation (http://www.shikikaku.com/en/question/)

2. Color Universal Design (CUD)- How to make figures and presentations that are friendly to Colorblind people – (https://jfly.uni-koeln.de/color/)

3. Color Universal Design Organization (https://www2.cudo.jp/wp/)