What Color is Best for the Walls of an Art Gallery?

"When displaying my oil paintings for sale, what is the best color for the walls on which the paintings will be hung? Is gray better than white? Most of the paintings are medium to dark in overall appearance." -- B

White has become the norm when it comes to the walls of an art gallery, but is it the best choice? Here's my answer to B's question...

• What color would you choose?