It absolutely should be in camouflage and be waterproof. It should also be fairly large. Since waterfowling is a "sit and wait" deal, you don’t have to carry the bag while actually hunting. However, you should consider how long and hard the trek to your blind is because you will be carrying the bag and your gun that far.

I’ve settled this problem by having two bags. One is large so I can carry lots of gear to easily accessible blinds. The other is small for the tough treks. Taking the smaller bag means I have to be more discriminating about what I think is absolutely essential for that morning’s shooting.

A good blind bag should have several separate pockets and maybe a compartmentalized interior, like a camera bag. That way your don’t have to dig through everything to find the item you want.