Well, it was definitely harder than it looks. The description on the game's page and in the game have not been totally clear to me, but I managed to figure it out. In the beginning I tried to change my colour by pressing R/G/B, but only found out later that you need to "find" the respective colour first. Just trying it again saved me the trouble of travelling all the way back to the red zone and suspect some actually do travel. To prevent this just add a little message on screen like "you can now switch to red at any time by pressing R".
The game play and level design works well most of the time. For me personally the colour switching is a bit too fast, so I tried to find a pattern like "four fast switches, then one that takes a bit longer" to figure out when it is safe to approach an enemy. But I guess you just have to react really quickly. In the end I managed to do it, but if you plan on make the game more accessible, either lower the changing frequency a bit or add an alternative way how to defeat the enemies (by introducing a pattern or some mechanic to force an enemy to a certain colour - you name it).
I see you chose Godot as your engine, and I'm happy about it. Consider uploading HTML5 builds as well, as those are more accessible for people just trying out a lot of submissions as they don't have to actually do download, extract, start. Also you should add a licence hint or at least link to the Godot licence/web page. Although Godot is free and open source, it still does have a licence you have to comply with. Also since your rendering text, you're using FreeType which comes with it's own licence. See https://docs.godotengine.org/en/3.1/tutorials/legal/complying_with_licenses.html