If you want to go for something other than the typical gameboy palette, as linked by taltuae, I would suggest the following:
https://lospec.com/palette-list/ayy4 (a very good palette by one of the hosts of this game jam)
https://lospec.com/palette-list/cosmic-cream-gb (good colour contrast, would likely be useful for a platformer)
https://lospec.com/palette-list/mist-gb (will provide a similar feel to the classic gameboy games if you're wanting a slightly different take on the typical palette while still maintaining the classic aethstetic)
https://lospec.com/palette-list/andrade-gameboy (a more desaturated version of the typical gameboy palette if you are going for a darker tone)
https://lospec.com/palette-list/coral-4 (this palette is useful if you need something more versatile and colourful for you vision of the game while still following the gameboy concept)
If you need anything more just set the filtering options to number of colours as 'exact' and set the limit to 4, there's plenty of good 4 colour palettes on the site.
https://lospec.com/palette-list
Of course, feel free to make your own from scratch or mix and match these palettes, the only limit is the number of colours.
I hope this can be of some help and good luck on the game jam :)