I apologize, but it is next to impossible tofix this. This seems to be a theming issue on Android 4.0.4 on your phone. The only way to fix this is to randomly try random solutions like this one: http://stackoverflow.com/questions/26843098/android-appcompat-v721-0-0-change-material-checkbox-colors
But I can't really test whether the solution actually works.
Hmm. How about the checkboxes in the Launch Quiz screen? Are those visible? Can you please give me a screenshot of a screen where the checkbox is visible for you properly?