I would recommend a medium pink or peach color, because if the dark purple and black are too close in shade, they won't stand out from each other. The black wall will look more like it doesn't match instead of looking like it was intentional. However, the pink can provide a nice contrast to the black wall, lightening it up just a little to make it cheerier and more comfortable. Any pink or peach paint would look great – or if you really feel like purple, you might consider a lilac color or something similar. If your furniture is white, you might want to try curtains with a pattern that's eithe