Lighting sprites that are black and white.

So I'm working on a game where the sprites are all white and black. I thought it would be interesting to add red torches that turn the white around them red, but I can't seem to add lighting without making the entire screen dark. If I add an ambient light it then just makes the torches not do anything. I get that colors add up to white, but is there some way to lights that perhaps subtract blue and green? Or just overpower white?