The big problem with red is that the enemy will see you before you see them in most instances. It also means that they are likely to know which side you are on immediately, while you might not be so sure about their identity (or might even be wrong.) Identification was a big factor in many ACW battles, particularly early ones. True open field, set-piece battles were rare. A lot of it was fields broken by trees, streams and hills as well as large tracts of timber.