How did you manage multiple background colors?
There are a few steps. First you have to manually add colours to your palette in the game data like so (these are comma separated RGB values):
Then you can assign a different tile or sprite colour to each of your tiles, sprites or items by adding 'COL [N]' to it in the game data:
The colours are assigned using 0 based indexing, so the first colour in the palette is COL 0, the second is COL 1 etc.
I also used this transparent sprites Bitsy hack. This allowed me to layer sprites over tiles to add extra detail. So for example, in the first sunset scene the background colour is pink, the sky and sea are tiles and the sun is made up of a bunch of sprites layered on top.
I hope this all makes sense! Feel free to ask if you need anything clarified further.