There's a very good writeup of the process in Ctein's book Post Exposure, which is a free PDF download on his website. Well recommended. Another write up is in Barry Thornton's book (I forget the name, the 2nd book...), using slightly different materials and method. Both would be suitable for color, Ctein's is written for color expressly. Agreed with 2F that it's really the best way to print color. I haven't made masks yet but plan to do so soon, probably this winter when there's less stuff to shoot and more time for darkroom work.