The Nintendo Super Famicom is capable of displaying 256 colours from a
palette of 32,768. These 256 colours are split into 8 palettes of 32 colours
each.

To change the colours the following needs to be done:

Loading the palette control register ($2121) with the colour number you wish
to change (0-255, 0=background).
Then load the colour into the palette data register first the low 8 bits,
followed by the high 7 bits (this gives you the maximum 32768 colours
possible $0000-$7fff).

Colour data is made up of 3 components (Red,Green,Blue) each of 5 bits (The
Amiga uses exactly the same system, but only using 4 bits per component).
Saying that, Nintendo being the stupid japanese idiots they are decided that
R,G,B wasn't alphabetically correct and so opted to store the bits as B,G,R.

                      00000 00000 00000
                      \   / \   / \   /
                       \ /   \ /   \ /
                        B     G     R

Examples:
~~~~~~~~~
         11111 00000 00000 = $7C00 (Bright Blue)
         00000 11111 00000 = $03E0 (Bright Green)
         00000 00000 11111 = $001F (Bright Red)
         00000 00000 00000 = $0000 (Black)
         11111 11111 11111 = $7FFF (White)

Easy, isn't it?? (But remember to load the lowest 8 bits first, then the top
                  7 bits).

Starr/QUARTEX