I’m at a loss on how you are using the paintFX hairSystemShape Node along with the Vray Hair Material. Are you somehow graphing them together using the connection editor?
I only ask because just hooking up the diffuse, secondary spec and transmission to the vray hair material, doesn’t appear to change the colors or use the color randomization field from the Hair System Shape node for paint FX. So I’m thinking you are graphing something with nHair colors that I’m not understanding.