RE: carb diaphram replacement color/material
While you're looking at those diaphragms, note the top pump diaphragm. Looking at the two little flaps in the top picture of the black diaphragm you can see a bend in the left flap. If you see a similar condition on the pump diaphragms in your carbs, replace the diaphragm. Those flaps must be dead on flat for the pump to work effectively. Bends or other damage to those flaps require they be replaced.