A small study focusing on the contrast of color complements. We describe form by the lightness or darkness of an object. When painting we use a colors complement to shade or shadow the form, to give it dimension. The complement green in this case must be seen in the red apple shadow and vise versa for the cloth. The lightest tones on an object are the highlights and even they have a slight influence of the objects complement color. Pumping a little green into the highlight gives it a real spark.
Using items that are opposite in color actually helps to see this feature of light. If a colors complement is not used in conjunction with it, the color looks flat or unnatural.