I just noticed that the foam around the dolphin is not affected by the screen tint, since the dolphin is only a Picture shown over the playable character's sprite.

@XBuster: Showing the HUD is quite simple :3
Whenever the player is teleported to a new map, I have an event show the blue boxes with slight transparency.
Then I use Common Events in the engine's Database to check the player's stats' current values (HP, XP, etc.) and that constantly show the appropriate numbers using other Pictures. This is not the best way to code it though, as it might cause some lag on older computers, but it doesn't seem to be an issue to anyone here.