I'm thinking about giana
I image well 2 optional copper backgrounds (one for the sky and for the cellars)
There may be enough CHIP memory available before address $1000 (if not used in game=>to check) and the game is not using the second copperlist. Which allows a fairly easy patch of the first copperlist........
I image 2 external files with just the list of colors for the levels with blue background and black background for easy modification & test
the custom copperlist should have a maximum size of 200*8 bytes
for one WAIT & MOVE command per line...
I'll think about it this weekend