A study tested two alternative theories about the relation of color and visual learning: that realistic color serves to facilitate retention of instructional material and that all color functions only as a coding device which facilitates storage and retrieval of information. It also tried to discern an interaction between learner IQ and color function. Two hundred and twenty four students from Pennsylvania State University were divided into treatment groups. All groups received the same instructional presentation but different visual accompaniments--realistic color drawings, non-realistic color drawings, black and white illustrations, or no visual supplements. Achievement tests were administered and compared with IQ tests of the students. Findings showed interaction effects between IQ and visual stimuli. Lower IQ students did worse on non-illustrated and non-realistic color treatments; black-and-white illustrations reduced achievement differences between IQ groups; non-realistic color served to increase learning only for high IQ students. (KB)