Add an easy way to disable or reset background color

[paaljoachim]

When one first selects a background color there is no easy to change ones mind and turn it off again. One has to try and select the same background color which is in the area one is in.

I am suggesting adding a way to add to all color panels a way to deselecting using a color. Going back to neutral. Resetting. As in having no background color. For instance in some instances I have seen there is a square with a red X in it. Instead of that there could be a reset button which just brings it back to how it was before one selected a color. Perhaps the first option in the color palate should be the red X or some other square to show that selecting the specific square brings transparency to the background.

Associated issue: #143