I think that is one of the reasons they did away with black, and sage (i dont think its there anymore, if it is dont get mad because my spartan has always been blue). It could give you the advantage because it is harder to see the players. From halo 2 red was very hard to see on beaver creek so it was an advantage there.
The best thing to do is just go with the color you like. Sure on maps like Ghost Town and Avalanche it makes a difference but that difference is minuscule and shouldn't prevent you from choosing the color you want instead of being unoriginal and going gray like everyone else.
It all depends on what map you are playing on and what colour your armour is. I being the colour light blue generally stand out from the crowd. I am perfectly fine with that because if you need to hide, you need to get better at halo.
It also depends on the armor your using, because if you're using the security helmet you'll still stick out.