Yes indeed, watercolour can be painted on black paper, specifically paints with opaque qualities, yielding interesting results. The process is opposite from painting on traditional white paper, working from dark to light, and lifting paint for dark values as required.

Campfire Under the Moonlight, 7″h 7″w [framed 12″x12″]
Worth the Wait, 8″h 10″w [framed 12″x14″]