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Since 1999, I have been teaching a course in Color Management and Quality Control as part of the baccalaureate curriculum in Graphic Communication at Cal Poly, San Luis Obispo. In the years that I have taught the course, I have had nearly 1,000 students, and I have required every one of them to take the Ishihara color-blindness test as well as the Farnsworth-Munsell color discrimination test (See my paper, An Analysis of Color Discrimination of University Students in the Graphic Arts from the TAGA 2009 Proceedings on the Farnsworth-Munsell test results). Shinobu Ishihara (1879-1963) was a Japanese ophthalmologist who developed the most commonly used test for color-blindness. His test is used worldwide, and is the basis of both medical and workplace vision testing for people in all walks of life. The Ishihara test is administered to both children and adults, and is valuable in determining if a subject has one of the two most common color defects, which are called protanopia and deuteranopia. Both are forms of red-green color-blindness, and they affect a small percentage of the general population. Ishihara's test, however, does not test for a rarer form of color-defective vision, that called tritanopia. Tritanopia is a blue-green color- blindness which affects a tiny percentage of the population (less than 0.01 percent). Dr. Ishihara clearly never encountered a person with tritanopic vision, though he does acknowledge the possibility of its existence in the booklet that accompanies his test plates.