Yep... Would help immersion. Unless I'm mistaken Il2 has the right colors. US 50 cal are red, so are 303s, M2 cannons and hispanos are yellow, so are MK108s and 103s, MG151/20 are blue, and somewhere in there I've seen spitfires shoot a mix of pink and yellow, I think. Whatever the pea shooters on the Il2 are, are green.
A long while back Fester had linked to a page with the full details on all WWII tracers, but it went down when I went back to look for it a year or two ago. It was a simple black background webpage with mostly orange font. If anyone has it archived I'd like a copy.