Based on your description, it seems that the tool you're referring to would help an artist understand color. The presence of a circle with an octagon in the middle and lines radiating outward, combined with the use of rainbow colors, suggests a focus on color theory, which encompasses concepts such as color harmony, contrast, and the emotional impact of color.
Additionally, the geometric forms (circle and octagon), along with their arrangement, could also touch upon shape and space. However, the emphasis on different colors suggests that color is the most prominent element of art in this context.
If this tool is used to explore how colors interact within the shapes and overall composition, it could provide valuable insights into the use of color in art.