By default, the Task Manager widget shows minimized windows as gray. I want to change the color from gray to black/darkgray, so that it looks like all other windows which are not minimized.



Konsole window is minimized, all the other windows (Sublime and Chrome) are not. I want to make it look like all other windows.
And way to do this?

The taskbar styling is determined by the currently-selected Desktop Theme, so you might try different Desktop Themes to see if there's another which suits your tastes.

Thanks, I tried to go to /usr/share/plasma/desktoptheme/ and change the Breeze-Dark theme's colors, but no success. No matter what I set the color RGB values, that part always remained a little bit lighter than the rest of the panel. Maybe the gray color is an image/svg file with transparency, but I am not in the mood to try to go further in the experiment.
For now I've downloaded a nice theme (called Sweet) which doesn't have this effect on the Task Manager widget's elements.