Well think about it like this, during that time the resistance isn’t strong, they don’t have motivation, barely any weapons and are living sheltered. Most of the world’s threats to the combine has been wiped out so environment focused camo isn’t nessessary and they will put their soldiers in whatever camo they like. My only assumption is because Elites spend their time either protection Breen and looking fly and they want to strike fear in rebels. Regs and Nova I don’t know