It would be a really great effect for black holes, magic spells and so on if an object could absorb light instead of emit it.
But i think this is too hard to implement. Isn't it?

I am pretty sure this already works-- just set mylight.red = -100, then mylight sucks out the red

this technology uses "nightbulbs"

yes negative light setting should work, if not a simple shader can do it.

Setting the light color to a negatie value will only effect entities.
The textures of the geometries are as bright as before.