Mixing pairs: ultramarine blue and burnt sienna

Stu­dio Prod­ucts ultra­ma­rine blue, Doak burnt sienna, Rem­brandt tita­nium white.

I mix these two often. They are not exact com­ple­ments, but they form a use­ful set of neu­trals. It is par­tic­u­larly help­ful that you can get a very dark neu­tral from them, which I often find to be a good sub­sti­tute for black.

Update

21 June 2008: For lighter neu­trals (grays) I tend to use ultra­ma­rine and raw sienna, which makes a more pure neu­tral. But for darks, burnt sienna and ultra­ma­rine is the way to go.