I found this on Wet Canvas from one of the members. I think from what I've read, thouogh, it depends on the brands of paints.
I mix my own! ;-)
Burnt sienna, and phthalo blue, or cobalt blue, or ultramarine blue, depending of the temperature, and granulation I want.
Hope this helps, bella. I haven't tried this..so I have no idea if it works.