Here is someone that has done tri-color, the site is in French but a Google translation is here:
Original French Page:
Instructions on how to make Autotype Trichrome Carbro prints (including recipes) + other methods to reproduce colour:
or you can try 3 layer Gum Bichromate prints as here:
I think that all the processes are somewhat difficult to do in a home darkroom except the gum bichromate the problem is achieving an acceptable color balance.