Color-blind subjects and non–color-blind control subjects were recruited by fliers and by e-mail postings at the Valhalla campus of New York Medical College. Color-blind subjects and controls were first tested using the Hardy, Rand, and Rittler pseudoisochromatic plates.5,6 Subjects were further tested with the Ishihara 14-plate test.7,8Color blindness on the Ishihara scale was defined as 2 or more mistakes on the first 11 plates, in accordance with the test's instructions. For inclusion into this study, color-blind volunteers had to show color deficiency on the Hardy, Rand, and Rittler and the Ishihara plates. To maintain consistency when viewing the photographs described later, color vision testing was done using a lamp with a 60-W soft white incandescent bulb. Color-blind subjects were classified as to red-green or blue-yellow color deficiency, and among those who were color deficient, as to severity based on the suggested criteria for interpretation of the Hardy, Rand, and Rittler diagnostic series of plates.5 Red-green color–deficient subjects were classified as having very mild, mild, or strong deficiency, and blue-yellow color–deficient subjects were classified as having medium or strong deficiency. Subjects with reproducible mistakes on the red-green or blue-yellow Hardy, Rand, and Rittler screening series of plates without errors on the diagnostic series were designated as having very mild red-green or blue-yellow deficiency, respectively.