You know the Game Boy by Nintendo, right? The gray brick with a dot matrix screen?
That thing uses two bits per pixel to color its screen, resulting in a total of 4 colors you can use for Game Boy graphics, typically going from lightest to darkest.
Here's a collection of 4-color palettes you can use for Game Boy art or emulation.
(Palettes without easily identifiable names will be given a name by me)
(Credit to SharkGuy for the Scolipede sprite and credit to Ryan Armstrong for providing a few of the screenshots.)
(This page is best viewed at 100% zoom on a 1920px wide monitor. Yes I know this website fucking sucks but at least I had fun making it!)
Example images: