Heh, no, it's not my eyes. On one background, the spreadshot type projectile just barely shows. On another type of background, the claw-shaped enemy projectiles barely show. I mean, a single one would be obvious, but when there are ten enemies and twenty projectiles and fifteen explosions constantly on the screen, telling which is which gets difficult.
But, like I said, I'm not going to tell you to change any of that. You went for a theme, and now you have it, and it looks good. It just isn't the best color scheme for such a frantic shooter. I have more complaints also, but those are purely gameplay related and have been around since Gradius, so I'm not even gonna got here...