Thanks for checking out my game! I wanted to keep the game free from any unnecessary HUD elements, but I'll add those instructions to the game description at least to make it easily available.
In terms of understanding what colors are available, that's actually built into the game already in a bit of an interesting way. The colors you can use are actually contained within your character's color. As you use colors to see the world around you, those same colors leave your character. So when you start off you're white. Then say you use green. The world around you lights up in green, but you lose that color and turn purple. There's a bit of a lesson around colors to be learned to fully grasp it. This also created a bit of a challenge around making sure you don't run out of colors, because if you use them all up you turn black which makes it difficult to see and navigate around you.
I understand the issue regarding color accessibility. It's something I personally care about, but I struggled to find a way to have this concept be more accommodating. Patterns are a good idea, but they'll only go so far in the game as you'll end up encountering objects in the game too small to place patterns onto. I like where your head is at though, and that's definitely something I'll put more thought into going forward.