(I made some alterations to the original artwork, trying to correct some mistakes)
Black COLOR can have an important role if you decide to make intermittent lights (intervals).
Question: So, why would we use fountains, colored torches and that kind of stuff?
Answer: Torches and Gemspark Blocks are a thousand times easier to make and use. The photontizer is an end-game feature created to make your buildings look better. Fountains can be used as a way to texture water and as a furniture.
Cool COLOR Ideas
Shadow COLOR - If used with the Photontizer it's going to emit a shadow light, blocking every light. Even holding a torch (or other source of light) won't emit light, it's still going to be dark, like an inverted light (Shadow Light).
If used with the Liquid Dyer, nothing inside of the liquid is going to be shown. Lights, players, enemies (Black Hole).
Negative COLOR - If used with the Photontizer it's going to emit an inverted light, inverting the color of everything on its range (Inverse Light).
If used with the Liquid Dyer, everything inside of the liquid is going to be inverted. Lights, players, enemies (New Dimension).
Saturation COLOR (Also Grey COLOR) - If used with the Photontizer it's going to emit a grey light. Everything on its range is going to be Black and White. (B&W Light).
If used with the Liquid Dyer, everything inside of the liquid is going to be Black and White. Lights, players, enemies (50's).
Invisible COLOR - If used with the Photontizer it's going to turn the tile, where the photontizer is, completely invisible (only the tile) (Invisible Not-Light)
If used with the Liquid Dyer, the liquid would still be there, but invisible (Fountain of Invisibility).
In this case, the tiles and liquids would only be seen holding a wiring tool.
Take a look at the Pixel Art I did for this mechanic (I tried to improve a little bit, but it's not the best sprite ever)
Some other cool ideas that inspired me. (One of them is mine)
I would love this mechanic to be implemented in the game, that would help a lot the builders (like me).
(You can also take a look at some other ideas I had for 1.3.1 here)