I hadn't thought of that. A system like that would be very interesting. If you have something on-hand, I'd be very curious about it.
So there are a few ways to do this, but which method is best depends on what is in your game.
As an example of a way of doing it without plugins (plugins can make it nicer):
If your game ever uses the tint change options, then it is more complicated, but you can add an item/skill/menu item that sets a flag on top of changing the tint. For each tint, you'd have an option (if you have plugins for it, you can have more flexibility) and selecting that option would set up a different flag (such as a variable).
The reason for setting a flag is so that when you do any tinting in the game, it will override the tint. Having a flag will allow the tint to be reset back.
You then put the tint changing as a common event to be called whenever the tint should be returned to normal (so instead of always returning it to 0,0,0,0; it can return it to a value based on the tint flag).
As a bonus with this, you can do things like having the tint change temporarily (You can even make that temporary tint be based on the selected tint) and have it change back later or even have puzzles and other elements change based on the selected tint. (For example, you could have it where water evaporates with a red tint; a blue tint washes away fire, yellow lets you sneak past enemies, green could switch to 'retro' mode with changed mechanics, etc.)
The reason I mentioned it is that your setup seems like it would work well. (Note: Screen tint and image tint are different things).
Oh, this seems very interesting. This is slightly different from the setup that I'm using, and I'm not sure I'm going to be able to have time to implement it in-game, but thank you very much for telling me about this!
If I come back to this project after the gamejam is over, then I'll see if I can wriggle it in.
Considering that it doesn't look like your game calls the battle function (as tint does affect the battle function. I actually had a game where one of the battle mechanics was related to your tint), it actually shouldn't take too much work to implement the basic portion of it.
If you don't use tint in your game, some relatively easy ways to implement (just the tint portion, not any related mechanics) is have some events in your starting area that allow you to change the tint, add an item to your inventory that lets you change the tint, or a skill that lets you change the tint.
It is definitely true though that you might not have time to implement it depending on how your system is set up.