From an artists's point of view, you really should create a second set of assets for night time for a natural look. Objects change the way they look in different ways when lit by different sources of light. There isn't really a quick filter you can use to simulate this in a sprite based engine.
Even with a 3d engine it is simpler, but it can take a lot of work to customize lighting for a proper night scene. This is why a lot of games opt out of having day/night cycles, sometimes it isn't worth the time investment.