Product Features Convenient Portable Comes with case Ishihara Colour Test Books The Ishihara colour perception test for red-green color deficiencies. The test consists of a number of colored plates containing a circle of dots appearing randomized in color and size. Within the pattern are dots which form a number or shape clearly visible to those with normal colour vision, and invisible, or difficult to see, to those with a red-green colour vision defect, or the other way around. 38 and 24 Plate versions are available.