Grid Terrain

Hi everybody.
I want to make a turn based rpg, but I don't know how to draw a grid on the terrain. I've tried the projector and I've also made a script that create a plane made of cubes but in both these methods I don't know how to change color of the tile (show where the player can go, the area of effect of the spell...).
Can someone help me?
(Sorry for grammar errors, but I'm not english)

 

I have created an asset that draws grids over terrain, and it works with or without Vectrosity.

Unity Asset Store: https://www.assetstore.unity3d.com/en/#!/content/35762