I want to point out that the console uses a (quite appealing [1]) fixed palette of 16 colors for all of its graphics. I think having a fixed palette is a great idea. I can see it helping would-be game developers overcome their initial art style analysis paralysis and helping ensure that the games have a recognizable "PICO-8" look.

[1] See http://i.imgur.com/1VOlxCt.png.