About to submit mine with my small indie studio (cold honey studios), definitely didn't achieve everything my team and I wanted to but I'm still so happy that we managed to finish something for our first game jam. Huge congratulations to everyone who completed their games, I'm so excited to see all the great things that everyone has come up with!
I don't believe that there was anything stopping the display of the Gameboy to be any colour, however they would likely have to be monochromatic. On a purely technical level I believe that the palettes that the hardware could display were purely monochromatic, with the proper Gameboy displaying a 4 colours green palette and specific variations having a 4 colours grey scale (this is from a very limited knowledge so feel free to correct me if I'm wrong), no idea the exact reason for this but is likely something to do with the technical capabilities. So, for a pallette that at least seems that the game boy could run, I would suggest that you could simply get a 4 colour monochromatic palette, such as the typical Gameboy palette, and hue shift it to the colour range you want. This will hopefully provide an authentic Gameboy feel. Another tip for keeping your colours Gameboy-like would be having a slight desaturation of the colours as I don't believe that the original game boy was able to display highly saturated colours. There's no right or wrong way of doing this and you can use any colours you want in order to complete this project.
Tldr:
While there wasn't any colour restriction on the hardware that I'm aware of, if you want your palette to be Gameboy-like you should pick one colour and make a monochromatic palette based off of that.
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/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 :)
It literally is peak gaming, there have been very few games that have affected me so profoundly. 10/10 game definitely worthy of the game of the second award.
