No, of course, it's an interesting thought. Colours do factor in, as the best camouflage in the thick woods is black, in the "thin" woods it's grey and brown, in an open field it'd be dependent on season and flora, so anything from a yellow to red and brindle could be an advantage and so on. However, at night, coats that're black, dark brindle and blue are the tried and true best of the bunch, with the black again being best for really dark spots with no moonlight, the blue being precisely ideal for moonlit terrain and the brindle being just right for either application, just like the wolf-grey/sable cover.