Set a particular CSet (Preferabily CSet 2 or 3)
If you are currently on the screen with a level color (other than Overworld), go to the Tiles (Quest > Graphics > Tiles) and edit any tile. There is a problem! The level color reverts to Overworld.
Tile editor issue, level color [798]
There is already a thread like this, and actually, it reverts to the main palette (The Overworld Palette changes if you edit CSets 2, 3, 4, and 9 in the main palette).