those are showing maximum unit size that can access that tile.
orange= no access, blue= 1x1, green= 3x3 tiles. other= 5x5 (this is the max size at the moment because of speed reasons)
they will have role only in the low level pathfinding, when units have to find their way very fast, depending on their size (and their other capabilities).

Free world editor for 3D Gamestudio: MapBuilder Editor