The Roth 28-hue test.

The Roth 28-hue test, first described in 1966, uses every third color cap from the Farnsworth-Munsell 100-hue (85-color-cap) test. Protans, deutans, and tritans exhibit slightly different confusion axes on the Roth 28-hue test and the Farnsworth D-15 test. These axes are illustrated on a CIE chromaticity diagram. The little-used Roth 28-hue test may be a good compromise between the D-15 and 100-hue tests, but clinical trials for verification are needed.