Problem

You want to manipulate the Lighting of your place.

Solution

Use the Ambient, Brightness, and TimeOfDay properties.

game.Lighting.Ambient = Color3.new(1, 0, 0)
game.Lighting.Brightness = .5
game.Lighting.TimeOfDay = '01:00:00'

Discussion

The Ambient property will change the hue of the ambient lighting in your place. In this case, we turned it to a red color. The Brightness property sets the brightness of the ambient light. The default is 1, so it set it to be a tad lower. The last property, TimeOfDay, sets the time of day in which the sky will simulate, in this case, we’re simulating 1 AM in the morning so it will be a dark sky.