Thank you for your support, I’m glad to hear you appreciate this plugin. Please feel free to let me know if you encounter any bugs or if you want to make suggestions on the next versions of the plugin.
The color scheme is actually set as default only when a new user registers; thereafter, the user is free to pick another one. I’ll work on this issue, and find a way to set it as default for all users without preventing them from changing the color scheme in their profiles.