___Remarks on the current UI___
6. When I change the color using the palette wheel: the input color is
changing on every click, but the ColorThemes preview does not reflect the
change, unless I close the wheel.
7. How can I undo the color change made with the wheel? Do I need to Cancel
the editor mode every time? How about an Undo?
8. How about a reset? This is actually done by Cancel for the edit mode.
___Other thoughts___:
When changing a variable color, we could show the relation between affected
elements by adding opacity for the rest of the elements.