Open the rom to a sprite or background to inspect,
then open the Tile Viewer and the Palette Viewer.
In Tile Viewer Touch the tile of the game that you want to find the palette to.
In Palette Viewer, Right click a color to inspect,
and then choose Memory Viewer to open the CG RAM.
You’ll see the row of palette colors— it takes 2 rows of bytes in the ram.
Copy the 2 rows of bytes that make up the palette. (Ctrl +C)
In Memory Viewer, change the View to PRG ROM (Program ROM).
Now choose to Search > Find that range of bytes (paste them into the Find).
When you find the palette you’re now seeing it in the ROM, not the temporary CG RAM.
So now you can edit a color in Palette Viewer (right click the color)
and it will change the value in the “cartridge memory”
versus the emulator memory.
Save your color edit to the game file (the ROM) with the File > Save As command,
like most other apps.
Repeat for all other variations you wish to make to the game.
Having multiple checkpoints of your work is the best practice!