This is how you get marine camo
This is what me and my friends have done and it worked for all of us.

1. Log on to callofduty.com
2. Go to your mw3 custom classes
3. turn xbox off
4.Go to one of your classes and change the camo to any one and send changes to game
5. turn xbox on and go to multiplayer and wait for it to get the message to receive new class
6. say yes and go to your class and it should be there.