Design an App Mockup

I have an app. We have not launched it yet. Since we used out previous app as a basic platform to make this one, the design and colors dont really match our current theme. I have correct english issues on the current app, but I need someone to, Make my app's color scheme more appealing. I do not want to do a drastic redesign, literally I want to just change the color of the buttons, text color (if necessary), and use the words I put in the powerpoint (for example, where it says "Funds" put "Payment Information". My programmer can do all this. We just want to make the colors work. Redesigning the app would be crazy since we have not launched it yet, it would cost too much and take too much time. The colors we have have no harmony or pattern. They are using red on buttons, which is not good unless the button is "cancel". You know what I mean. We could try losing the colors altogether and just coloring the text. I am open minded, i just want something that looks good.