I played with this idea for a while, but ultimately left it alone since for various reasons I found it a bit too complex for what I was trying to accomplish with this tileset (for example, CONGRUENT doesn't have several "border" tiles since at that resolution they wouldn't be visible/would be hidden behind other tiles; also, it would mean creating terrains for every color variation which was just too time consuming for me)- there's always an option of creating the terrains yourself, though :)