Nonvisual demands of tests affect vision test results in children. 150 children (79 females and 71 males, 5.3-12.7 years of age) were examined. Isoluminant Blue, Yellow, Red, Green, and Black and White thresholds were established with a four-alternative forced-choice and pseudo-10-bit system with adaptive staircase and gaming elements. Where Threshold = b(0) + b(1) * age(-1), b(1) for RG = 6.26 +/- 1.90 (95% confidence limits), Achr = 3.96 +/- 1.07 and BY = 12.48 +/- 2.76 were significantly different. The noncolor demands of the test are the same for RG, BY, and Achr, so the later development of BY discrimination is not an artifact of the test. (c) 2018 Optical Society of America