probaly grey or whit cos it blends in mor. not red or yellow cos then you stick out an will get killed. so grey. if you want to live.
I choose red and purple, because it looks cool to me. It also works well in Reach with Elite armor, which blends it and makes it look like something an actual elite would wear
I usually have silver set as the secondary and white set as teh primary, but i usually change teh primary around indiscriminately. Silver is pretty much always set as the secondary color though
BLUE AND WHITE!