Art class today: we had to paint our live model with contrasting colours (those on the opposite sides of the colour wheel, like blue-orange or yellow-purple). In my case cadmium red and phtalo green.
Using these colours results in enhancing each other, red becomes even more red when placed next to green.
Secondly: when mixing opposite colours you get the most beautiful greys and blacks.
Here I show three stages of the painting: the charcoal drawing, the high contrast basic painting, and finally the adding of red-green greys. I was suprised by the result: here it looks like the model got a heavy sunburn, but in reality the painting looks more harmonic than on these pictures.