Well not help witht the actual game, but in Halo 3, can you customize your Master Chief's color like in Halo 2? And just to inform you, I don't have Xbox Live, if you need that to customize your Master Chief.
Well, I haven't tried yet, but I don't know if you can customize characters without Live. Since I have Live, I haven't bothered checking.
Look around.
Live is unneccessary. I believe you hit start while in a multiplayer screen, scroll right and "Appearance" should be right there. It's in the menu where you choose maps and whatnot before a game.
Well in campaing you have to be green on live you get to cuztumize or in Custume games
On Halo 3 menu...
Press Start > Settings > Appearance.
There you go.