Unlock every camo for an entire class of weapon. Basically, you have to get gold for every SMG or whatever class of gun/weapon you want diamond in. You can't unlock it for just one gun. Has to be the entire class.
There's a list of challenges you can see when you equip your camo. For guns it starts as x amount of headshots, then x amount of kills with no attachments/perks, bloodthirsty, etc
I'm working on diamond specials. It's a bitch. I have a gold knife so far and working on crossbow. Crossbow is really fun. Especially with tri-bolt LINK
This post was edited on 12/21 at 7:49 am