[GAMEPLAY] Health and Mana at bottom of screen black?

This has happened once before, and since I use it often, it's annoying to not have it visible. Basically, the mana and health (green and blue) bars become black. They still have the red thing when they go down, but they are still black. And it's annoying! I have no idea how to trigger this or how to fix it or why it happens or what the side effects are. See screenshot for example.