During adaptation, two different letter strings (each five or six letters) were presented to subjects alternately, one in green and the other in magenta. The extent to which these letter strings subsequently elicited a color aftereffect was assessed. In different experiments, the chromatic letter strings consisted of words and nonwords. The results indicated that letter strings that form English words can contingently elicit a color aftereffect. This was the case even when the words were anagrams. There was no evidence that nonword letter strings could contingently elicit such an aftereffect, even when the nonwords conformed to English orthography. The results are relevant to understanding other contingent color aftereffects (McCollough effects), illusory color noted by computer operators who work at monochrome (green or amber) displays, and the processing of text.