Colours

Using the complementary colour instead of black to darken a colour makes for a more interesting painting as our eyes are naturally tuned to complementaries – so the use of complementary colours throughout a painting intensifies contrast. For example, ultramarine blue and cadmium orange mixed together can produce a colour quite close to black – so try using a bit of ultramarine to darken your orange, or purple to darken yellow, or green to darken red, an vise versa.
There is a simple experiment to prove that our eyes naturally see the complement of a colour: Take a plain white sheet of paper and put a red dot of colour in the middle of the left half. Stare at it for about 30 seconds, then look into the middle of the blank half of the paper. You should see the complementary of red appearing. (the variation of red would yield different results – a red with a bias to orange would produce an aqua green, while a red with a bias toward purple, would produce a more lime green). Try doing this with other colours too. This is an experiment we do in art class all the time.