Nope, only four. That's only the case for borders (which the jam host said was OK because the engine won't let me shrink the size. (And loading screens for that matter if you don't have a fast computer) The palette I used is color hex's gameboy color palette done by yusdotcom (with the exception of the grey color.) I promise you I use 4 colors, and just use contrast and cross hatching. By using these tools you can create images with more depth and complexity, while still using four colors. You can check my code or screenshot the game to check!
The logo uses more than four colors though, but in-game the logo is different so it's fine.