Some of the Uniforms by Ranks
Everything about the British seemed to boast their power to the Americans. How organized they were, their matching uniforms, their size, their guns, their cannons, their generals, and even their hats all seemed to be intimidating. Did they do this on purpose? It seems as if the color wasn't quite to intimidate as much as to be visible amongst themselves!
The flashy red coats and attractive yellows and plain whites were to help distinguish British from other British on the battlefields! All battlefields at the time were smoky with gun powder and dust and dirt from all of the horses and men kicking up dirt, from the cannons and guns and such. The British knew the Colonists hadn't the money to spend on proper uniforms (plus, they did, so they figured, hey, why not show off a bit with bright, luxurious uniforms?), so they took their prior knowledge of gun powder and spun it with the recent fashion - brightness - and managed to pull out the idea of seeing themselves in battle.