I usually undercoat my canvases. Although I sometimes use light grey/blue or beige, I usually use a light rusty orange. Here is the recipe:

* indicates required; "Part" is used instead of a specified amount, because I mix different sized batches depending on how many canvases I am undercoating. All "parts" are approximate and are varied for effect.

5-6 parts Raw Sienna*

1-2 parts Burnt Sienna*

2-3 parts Naples Yellow

1-2 parts Yellow Ochre

1 part Cadmium Yellow

5-10 parts refined Linseed oil*

Mix paint thoroughly and add enough Linseed oil for the paint to be a liquid similar to wall paint.

If I need a lot, I will combine everything into a water-tight jar and shake to mix thoroughly. Apply the liquid in a thin coat, and as the liquid gets used up, add more linseed oil to the thicker base of paint that is at the bottom of the jar.