Hi there!
I guess I miss your comment here. Sorry. You can try to check the sample project to see how I did it. But basically, this:
I check the hue color value of the event, and based on that, I change the hue color to the opposite value. On the sample project, I used events 20 to 181.
But that was just my case. You can do it with only one character if you want. Let's say the player, so you should use: $gamePlayer.hueColor, for example.