mmm you cant do it so every block gets its own colour the way i do it is to make a chequered material, with 10x10 grids and apply it to the model, to get dir of distortion, use unrap uvw modifyer, and select a column of faces, two faces wide should be fine, planar map, move to one side.... then select the next column, planar map, stitch to the first. and so on, then when your happy that there is no distortion, export with textporter, and apply that image to the model....