Don't know if many of you have heard of the Zorn palette. Basically Anders Zorn used a very limited palette of colours to paint his portraits, the idea is that the colours are more harmonised and the difference in colour values is less jarring. Here's the palette.
Ivory Black -flattens colours and gives a blue when mixed with white
Yellow - But some people steer away from yellow in flesh tones and just use Yellow Ochre
So the grid above mixed pure colours across the top and mixings of white moving down the scale.
I tried this last night and was amazed the number of colours I could achieve. I tried it without yellow and didn't even think I needed it when painting.
I usually only use around 8 colours when painting
Try it for yourself I think you will be amazed