A standing lamp is a furniture item that produces light at 50% up to seven squares away.
Placing standing lamps in dark rooms eliminates the debuff "In darkness". If placed outside without any roof, the lamp may short circuit with rain.
There are three varieties of colored light: red, blue and green. The functionally is identical to the regular standing lamp but an aesthetic variant.
By using colored lights near each other, you can combine the colors.
Using multiple lamps close to each other also gives the appearance of a more well-lit area, though this has no actual effect in-game.