We have many different color patterns and don't change them for war, however the Decepticon Seal is prominently painted on each citizen.
Not that anyone could miss that the giant sapient transforming robots raiding their refineries are The Decepticons, anyway. We wear our Seals out of pride more than as a means of identification.
If we find ourselves actually needing camouflage, we have the ability to turn on systems that allow light to be reflected in such a way that we're nearly invisible. However, we prefer to just target enemies that stand no chance, like humans, and let them gape in awe at our might!