If you are really working on making this into a game you might want to reconsider your approach.
In games one of the most important things is that things are readable. In a shmup this is even more important than in most other genres as to avoid frustration.
For example on the dark background, would we see the player shot? Do you think the little rockets are big enough to be seen quick enough?
Also I think the resolution you have going is a bit small, you are not making this for some 10 year old cellphone, are you?
Look at Guxt
It uses 6 or something colours (apart from some bonus items like that little red duck).
For the enemy shots he mainly used that single orange also used for the PAUSE text. To make them stand out, because this is a good thing to do when it comes to gameplay. If the player will get hit by something he did not see, repeatedly, he will get frustrated and stop playing your game.
Guxt also has a resolution of 120x160, which I would say is about as tiny as you should be going (or well 160x120 if you got horizontal) with a shmup, really, there needs to be some real estate to dodge around in. The res you are currently at would make things feel cramped.
As for the colours you also need to make sure everything always stays distinct, background and foreground. In your top screen it looks like those mountains would be obstacles which kill you if you crash into them. If that is the case, cool, if not you made them too dark. Google for Guxt and download it, it's freeware, and look at how Pixel did stuff, the graphics are fairly simple but the priorities work well and stuff never gets unreadable.
Hope this helps.