A study tested two alternative theories about the role of color in visual learning: first, that color provides an additional dimension of realism which results in the learner attaining a more complete image of the object or event and second, that color functions only as a coding device which facilitates the storage and retrieval of the image. Two hundred and twenty four students at Pennsylvania State University were randomly assigned to treatment groups which received the same verbal instruction but different visual supplements--black-and-white drawings, realistic color drawings, non-realistic color drawings produced by means of photographic reversal, and no illustrations. Achievement tests administered to the students immediately after the instruction showed that in those cases where instruction with accompanying visual materials was superior to instruction without visuals, realistic color drawings were most effective in facilitating achievement. No significant differences were found on delayed achievement tests administered six weeks after the instruction. (KB)