2-bit color

4-bit color is a color depth that can allow for up to 4 grays, or 4 colors assigned by a color lookup table (CLUT). This is referred to as "4 colors" on classic Macintosh systems, and the CGA standard by PC users.

Color palettes
When the cost of was high, early computers used color palettes to improve the appearance of graphics with a limited number of colors.

Apple Computer
Though Apple Computer's early Macintosh systems supported a 4-color or grayscale mode, most were capable of displaying more colors. The only system to ship with a maximum 2-bit display configuration was the PowerBook 150.

IBM
implemented the standard on their first.

NeXT
NeXT's first NeXTcube computer implemented support for a 2-bit grayscale megapixel display.