No one has heard this saying before, because it's new-- but, the phrase has a hidden meaning. Black, being a color that really only has one shade to it-- however, is worth two in the hand. In life, many things go unnoticed-- they become one-dimensional. When man handles an object, and creates-- the value of it goes up. For instance, take a rusty old bike, add a shade of paint to the body-- and suddenly it's worth double!! Or, raw-food when cooked-- suddenly becomes edible, as restaurants can then charge more... Any deviation of the idiom-- would be absurd.