## Summary of the Pull Request
This PR fixes two of the components of #8765.
> * [ ] Edit a color scheme -> Hit 'apply' -> the selected color scheme resets to the first color scheme in the list (instead of the one just edited)
This was fixed by storing the navigation state as a singleton in MainPage, and having the color schemes page update the selected scheme on that singleton. That way, a subsequent navigation to the schemes page could re-use the existing state.
> * [ ] The buttons turn gray on rollover covering up what color I'm looking at (I have dark mode)
This one was tricky. We're binding the resource for this button, to the color the button is bound to. We're also running a converter on that color, as to change the alpha slightly. This allows us to still have visual feedback on pointerover, without obscuring the color entirely.
## PR Checklist
* [x] I work here
* [x] Tested manually
9293867a06