I really like the idea of different colored bullets affecting your ship in different ways. Though, I wish that had a bigger impact on the gameplay. I could picture an expanded version of this where the gold perhaps gives you some sort of dodge and the red gives you the explosion ability, as examples. Something that feels more substantial to the player as they play.
The simple color scheme made the game very readable even when the screen was full of bullets. Also, having the game being themed around switching allegiance between heaven and hell is really cool. I got the Hell ending which is apparently the bad ending, haha. I feel like you could do a lot of cool things visually and narratively using this theming, such as the gold shooters being angels firing rings of light and the red enemies shooting red hellfire. That is if you choose to expand on this concept.
Overall, nice job! Cool idea and great theming. I would definitely like to see more substantial differences between which allegiance you're in if you decide to revisit this project.