For mental health professionals, art assessment is a useful tool for patient evaluation and diagnosis. Consideration of various color-related elements is important in art assessment. This correlational study introduces the concept of variety of color as a new color-related element of an artwork. This term represents a comprehensive use of color, which is a trait that is usually subjectively assessed by a rater's personal knowledge, experience, feeling, and intuition. A sample of children's crayon drawings (N = 52) were evaluated both by human raters and also by a computer system that rated the variety of color present in each artwork by automatically detecting the number of colors used and the length of edges between colors. Comparing the human ratings with the computer ratings showed a high correlation of the results, leading to a conclusion that the computer system can be a useful aid for art assessment by human raters. (Contains 5 figures and 2 tables.)