There are 2 banks (one usable at a time) of 256 palettes available. Each palette has 16 entries, the first is the transparent index ("color 0"), the 15 others are real colors, made of 16bit RGB definitions. Palettes are located at $400000 in the 68k memory map, they're physically stored in the palette RAM.
The bank used can be set by writing a byte to registers REG_PALBANK1 ($3A000F) or REG_PALBANK0 ($3A001F).
The maximum number of colors on screen without RLI tricks is 256*16=4096 (out of 2^16=65536).
There are two special colors used:
- The first color of the palette bank ($400000) is the reference color for the video output. It has to be $8000 (black).
- The last color of the palette bank ($401FFE) is the backdrop color (the color of the backmost layer on the screen).
D R0 G0 B0 R4 R3 R2 R1 G4 G3 G2 G1 B4 B3 B2 B1