For completeness, I’m adding to @awesomerobot’s mockup:
Note the buttons and check boxes at the bottom.
The 
, 
, and reset to default buttons are from the Settings UI, where each value is saved individually and immediately. But I don’t think we want each color value to be saved to the server immediately like that. Colors will be saved with the Save button at the bottom like the rest of the customization tabs.
So I don’t think we need the . But an undo button that puts back the saved value would be useful.
What does reset to default do?
- use the default value from variables.scss?
- if a built-in theme was chosen, get the value from that theme?