From Sega Retro

A palette is selection of colors which is used in an image. Rather than defining a color for each individual pixel (such as in 24-bit color images), palettes are used to link pixels to color data by way of an index reference. Graphics in Sega Mega Drive, Master System, Game Gear and Game Boy Advance games all use palettes.

Mega Drive palette

Main article: Sega Mega Drive/Palettes and CRAM.

Master System palette

Consists of 16 colors, each represented by eight bits (a single byte) in the format 00BBGGRR, where BB = blue; GG = green; and RR = red. The BB, GG and RR can be any of the following values:
Master System Palette.png
  • 00 = 0
  • 01 = 85
  • 10 = 170
  • 11 = 255

As such, the highest palette value is 00111111, which is 3F when converted to a byte.

Game Gear palette

Consists of 16 colors, each represented by two bytes (four nybbles) in the format GR 0B, where G = green; R = red and B = blue. The G, R and B can be any of the following values:
Game Gear Palette.png
  • 0/1 = 0
  • 2/3 = 36
  • 4/5 = 72
  • 6/7 = 109
  • 8/9 = 145
  • A/B = 182
  • C/D = 218
  • E/F = 255

Game Boy Advance palette

With 256 color indices for 4 backgrounds and 256 color indices for sprites, the Game Boy Advance uses the BGR555 format (15 bit colors). One color index contains two bytes (5 bits per component): 0BBBBBGGGGGRRRRR. The Game Boy Advance also has support for RGB mode where one pixel on the screen is represented by the RGB value and not by an index, so you can use images with up to 32768 colors.