Up to now we've reduced our palette in order to simplify the effect of "blocking in " dark, mid tone and light areas. When we try to add more hues to the painting it is harder to retain the effect of modelling with light.
We have mixed a muted palette from primary colours and so hues appear to retain their colour without destroying the harmony of the painting. This Sickert painting is a good example of this.
if we want to increase the saturation of the colours (how bright they appear) we can limit the range of our colours to create an analogue palette as in this example by David Park using reds and oranges for the figure.
Matisse gets away with a greater range of primary hues in this painting by keeping the value contrasts to a minimum between colours so that if you squint at the forehead you can hardly tell there is a change in colour.
In this Lucian Freud he is balancing the warmth of the skin tones (yellows, pinks and oranges) with a cooler greenish background which he also uses on the body to "cool down" the overall effect.
On Thursday we can try mixing up an analogue range of warm colours, bearing in mind that we will still need to make use of blue to complement it.