Seeing the complementaries in the shadows.
This is a slightly different look at the warm-cool aspect of color. Many years ago, I read in one of the artist magazines, a statement that: “if the light is warm, the shadows are cool, and if the light is cool, the shadows are warm.” I puzzled over this for some time. Now, let me give you a head start on this concept. If you look at a landscape on a bright sunny day, the greenery hit directly by the sun’s rays is a warm green, while that in shade is a cool (dark) bluish green. If you look at the same landscape on a cloudy day, the grass hit directly by the cool light will be a somewhat subdued green, while the shadowed areas would be a warmer green, (perhaps with the addition of orange tints.
This is also applicable to portraiture. I was interested to find, on a visit to the National Portrait Gallery, that some portraits were painted with highlighted areas in warm orange tones and shadowed area in cool grayed tones while other were painted with the lighted side of the face in cool flesh tones and the shadows in warm brownish tones, and that each worked equally well!
For example, the portrait (below) of John Quincy Adams has cool highlights and warm shadows, while the portrait of James Cagney has warm highlights and cool shadows.
Set up a simple still life with some fairly definite primary and secondary colors (fruit and vegetables are good for this, like bananas, tomatoes peppers, etc. Set up good directional lighting so that you see some strong shadows. Now, look for the complementary colors in the shadowed areas. (Hint: if you still see just grey, try mixing the complementary color in with the primary color to produce the shadow.)