Palette

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

According to the Oxford English Dictionary, "palette" didn't appear until the 19th century. "Pallet" is the original, correct spelling. However, both are correct today, and "palette" is more commonly used.

Megadrive Palette

Consists of 16 colours, each represented by two bytes (four nybbles) in the format 0B GR, where B = blue; G = green; and R = red. The B, G and R can be any of the following values:

• 0 = 0
• 2 = 32
• 4 = 64
• 6 = 96
• 8 = 128
• A = 160
• C = 192
• E = 224
• (and in rare cases, F = 224)

Pixels reference these 16 colours using a single nybble. 0 refers to the 1st palettte entry (which is normally transparent), 1 refers to the second entry, and so on.

Master System Palette

Consists of 16 colours, 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:

• 00 = 0
• 01 = 85
• 10 = 170
• 11 = 255

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

Gameboy Advance Palette

With 256 color indexes for 4 backgrounds and 256 color indexes for sprites, the Gameboy Advance uses the BGR555 format (15 bit colors). One color index contains two bytes (5 bits per component): 0BBBBBGGGGGRRRRR. The Gameboy 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.