|Wikipedia has more information about color depth.|
Color depth is a term describing the number of bits used to represent the color of a single pixel in a computer display. This concept is also known as bit depth or bits per pixel (bpp), particularly when specified along with the number of bits used. Greater color depth gives a broader range of distinct colors. Along with monitor resolution, it is one of the two factors determining how much video memory a Macintosh uses. Macs can be set to one of several color depths:
- 1-bit (2¹ = 2 colors) monochrome/black and white
- 4-bit (2⁴ = 16 colors)
- 8-bit (2⁸ = 256 colors)
- 16-bit (2¹⁶ = 65,536 colors), called "Thousands" in the control panel
- 24-bit (2²⁴ = 16,777,216 colors), called "Millions" in the control panel
Because memory is most conveniently accessed by programs in even multiples of a byte (8 bits), these are the only color modes supported.