I downloaded the app and I can tell you one thing that I noticed directly. these instant transitions, of course between red and green it has to be like this, but i think that you should add a transition like a soft fade or swipe between the other screens to make it more appealing for the user. And what you could do is giving the background a paper like texture(as if you put a semi transparent paper picture over the screen in photoshop).
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?