Get vertex color on collision or raycast

Is it possible to get vertex colors from a (non-terrain) mesh, maybe using raycast or collision? I'm designing a game with a terrain mesh onto w$$anonymous$$ch I have painted patches of grass using Ikari's Vertex painter. The t$$anonymous$$ckness of the grass depends on the vertex colour - black for no grass & w$$anonymous$$te for dense grass with shades grey for in-between densities. If it's possible I'd like to write a script that can determine the density of grass at a collision point by returning the vertex colour. Thanks in advance for any $$anonymous$$nts/advice.