Add a color chooser for the drop down list of tabs

[itewk]

It would be nice to be able to choose the colors used in the drop down list of tabs. Specifically I would like to choose the color border used to highlight the active tab, the color border used to highlight a tab I am hovering over, the background color for the active tab, the background color for the tab I am hovering over.

[shapkarin]

I think this pull request also can help to add color picker later.