Open fabrics, such as military netting, are your best all around choice. And in the case of camouflage, the adage rings true. Build your blind from natural components. If you are posting from within a cattail swamp, weave cattail blades in and out of your netting. Mix in a few cattail heads to break-up the pattern.
Some hunters construct their entire blind from natural materials.
Waterfowl commonly circle you and your decoys several times before committing to a final approach. Often, at least one of their passes swings right over your blind. In many cases, they detect unsafe conditions, and quickly bail out of the area. Their view from above likely reveals warning signs, i.e. empty shell casings, a brightly colored flashlight, beverage containers, a gas tank, and other unnatural items. A camouflage roof, or inwardly angled sides, reduces or eliminates the potential for spooking overhead ducks and geese.