The issue with setting custom slice colors on all categories (not just the first one) has been fixed already for some time.
Here are screenshots where default colors are replaced with custom colors for different categories: (Version 1.0.9)
Category3 again with USA in red color:
Category3 again with USA in blue color:
There has been cases when removing a visual from report and deleting it from visualizations and importing again can help. So if you are still experiencing this issue, then I would suggest you to try this.