First, this might be a railclone thing, but i'm also looking at forestpro. so starting here.
i've attached a screen shot. I have manually created the type of pattern i want, the green and blue carpet tiles to the right of the two orange lines. the idea is that the carpet tiles go from the grey-only tiles to the tiles with the blue fade, then to the solid blue tile then back to fade out again. then repeat further down but fade to yellow/grey carpet tiles.
you can see the railclone i attempted to start. with that it's really good, and i can do completely random material IDs, but i need the solids in the middle - where the actual door are, so the solid colors make a path of sorts.
also, i have to be careful about materials, because i use IRAYPlugin from Lightworks Design and it doesn't like forest materials