I just finished reading What Painting Is by James Elkins. It is about the link between alchemy and painting. There are some interesting ideas especially when he talks about the materiality of painting. He talks about how painters used to mix their own pigments using raw materials from the earth and follow recipes that were passed to them from their mentors. They would use sulphur, copper, iron, lead, etc. Each colour has a different "personality" because of the nature of the material from which it is made and they react in different ways to each other and to the medium (linseed oil, etc). It would explain why I can never get a fully saturated lemon yellow and why a touch of cadmium red can overpower your picture.
There are many good tid bits about painting (if you can get around some of the more out-there ideas such as the hermaphrodite being the ideal Christ bride as the symbol of the insanity ?!?). One such tid bit is that painting is thought in liquid form.
Another tidbit: a painting is finished once you can no longer tell which colour is on top of which.
I think I'll try to find this book on Abe so that I can underline it and mark it up . . . and then share my recipe of turning lead to gold with you :)