In Halo 4, there are various different armor skins in the game, however they don’t work like some people have thought they would.
Armor skins in Halo 4 are tied to specific armor sets, so you can’t just apply the Web skin you got from your Amazon pre-order for example to your other armor sets.
There are different armor sets in the game with skins you can unlock however. You’ll notice skins on armor because they are named like this: Recon SURG. This means it is the Recon Armor, with the SURG skin attached. Some armor sets don’t have any skins tied to them at all though.
Check out my complete guide for unlocking armor sets in Halo 4 if you’re looking for more armor to unlock.