Limited palette is a technique for painting portraits and reducing the amount of mixing and it is a good way to keep your values in check without having think too much about the temperatures.
the palette is very simple.
Yellow ochre, venetian red, ivory back, titanium white.
then the mixed colors you create a range that is more manageable.
yellow ochre+ a bit of venetian red+ white = flesh
Venetian red + white = Cool pink
Venetian red + ivory black+ white= Purple
Yellow Ochre+ ivory black = Green
Titanium white+ white = Gray (looks blue next to a warm color)
Venetian red+ ivory black + Yellow ochre = a rich warm umber.
add cad red cad orange and or ultramarine.