John F. Carlson

“To experiment with this principle, take a white piece of cloth and a brilliantly colored piece and lay them out on the grass where you can study them under different light conditions: sunlight, grey day, moonlight, twilight. The tone of the white piece will be more easily noticed, but you may be sure that the changes that affect the white are also present in the brilliant color, but seen with greater difficulty. Much will be gained through this study. It makes no difference what kind of art work you are employed in doing; the study will sensitize your “color-eye.”
― John F. Carlson, Carlson's Guide to Landscape Painting