All plastic provides the vapor barrier needed to trap condensation from a solar still/transpiration bag. Whether black performs better would have to be tested. The biggest reason clear plastic in used in the military is because you can easily see how much condensation has been trapped without opening the bag/removing the plastic to check on it. Every time you check, you release the trapped moisture (like checking the pot on the stove). I'm not sure you would want hot plastic anyway, since the condensation builds because of the differential of heat between the earth/plastic, or leafy tree limb/plastic. It may work fine, but not being able to see the progress without checking is not worth it for me. Great question... keep the gears turning!
George