Add Color Adjustments to Layer Settings

Being able to add color adjustments to entire layers would be extremely useful to many different types of maps. For example, if someone is trying to make a cave map and they need to adjust the brightness on the lowest layer, they have to go into their textures and tweak every single one of the used textures. With this feature, they would be able to go into the Layer Settings and be able to adjust the the entire layer's brightness there.

Adding something like this would be useful is a variety of maps in most, if not all styles and would assist in making the map-making process go smoother.

(Idea crossposted to Champions)