Currently it's impossible to set a tab's color to fill the complete tab, only a small area is filled, like here
Perhaps, some day, will it be possible to get the full tab filled and to set the font's color, too, on a per tab base?
Setting the font color may be necessary for e.g. a white filled tab to set the font's color to black and vice versa.
An option to switch between the current small bar and a full size coloring will do the job for those who are already acquainted to the current behaviour.
That limited the colors you could use. (Your text color had to remain readable on top of the chosen tab color.)
And it didn’t work well with different states. (Inactive, hot, active states need to look different. You also need to be able to see which tab is active vs the others, which is difficult if they’re all unrelated colors.)
Changing it so the tab’s color (if any) is used as an accent down the side instead of filling the whole tab fixes those problems, and I can’t see us going back to how it was.
