If you don't mind, I'd like to give you my opinion on this.
You shouldn't mess with OS UI stuff like this, it will just confuse the user. Now the user's system will have checkboxes with 3 states, on/off/yours. As a user I totally agree with you that the off state in Android is not very clear. But changing in ONLY your app will just make things more complicated for the user. Imagine if every developer changed the checkbox, it would be unmanagable... As bad as it is now, at least it is coherent.
The other point is that you can expect the OS to change the implementation of the controls making them clearer, and yours out of place (still).
Now, building a theme that replaces ALL of the checkboxes on the system, and that is intalled with the users consent is a different story...
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