And let me give credit to artist Daniel Greene for starting me on this path. He teaches this approach in his workshops, and it has made my whole process more efficient. The paint colors I use are based largely on his recommendations, with alterations depending on what I am painting.
The palette consists of:
White (usually Flake White)
Blue (Prussian, Ultramarine or Cobalt)
Cadmium Yellow Medium
Cadmium Red Light
And from this I mix:
Cadmium Red Light + Raw Sienna, + white to make a series of tints
Venetian Red + white
Yellow Ochre + white
Yellow Ochre + Burnt Sienna + white
Burnt Sienna + White
Then two greys, made from:
Raw Umber + white
Black + Raw Sienna + white
Two browns, made from:
Alizarin Crimson + Sap Green, + Cadmium Yellow
Sap Green + Alizarin Crimson, + cadmium Yellow
And some cool neutrals:
Raw Umber + Yellow Ochre, with varying amounts of Burnt Sienna added.
This takes me about 20 minutes to mix these, a good warm up while I drink my coffee and decide what to paint first!
This is how I mix the paint, adding a bit of white to some of the previous tint for that color combination until I have 4-6 tints in a row.
I will put the whole palette in the freezer overnight and that way get a few days out of the paint before having to put out more. These shades cover a variety of skin tones, and get my portraits going quickly in the right direction.
See full post here: Elizabeth R. Whelan2014-04-04.