Well. As so often when I'm on research, I stumbled accross an article that really puzzled me.
Have you ever wondered why uniform colours switched from all the bright colours to a handful of colours during the Napoleonic era and after that reduced more and more to reach grey/darkgreen/brown in WW1?
The answer to that maybe not the size of armies, nor the cost of colours and not all the pomp and circumstances, but simply the improvement of firearms, especially rifles. The more capable the weapons and their users became, the more it was necessary to give out grey/green uniforms to the troops in order to reduce combat losses.
That alone doesn't seem to be that much of a sensation, but what astonishes me is to find out that it really makes a difference for the aiming capabilities of a rifleman whether the target is dull grey of blood red, meaning that a red jacket is more deadly then a grey one just because of biological reasons...
...read more here: http://www.warof1812.ca/hamilton.htm