[xmonad] A third border color for the last focused window of a non-active screen

[Mauro Stettler]

Hi list

I have a question regarding the colors of window borders. As far as i
can see there are the two values normalBorderColor and
focusedBorderColor in the config, which define the focused and
not-focused colors of window borders. At my workdesk I have a
dual-head setup, so I select the two screens with mod-w and mod-e. Now
every time I select the other screen the window of this screen which
has been focused when i left the screen gets focused again. So my
question is, is there any way how I could choose a third color for the
last focused window of a screen which is not selected at the moment.

Like for example in the following scenario:

- I have 4 windows on each of the two screens
- The right screen is selected and its top right window is focused
- Now i select the left screen, so the top right window of the right
screen gets inactive and the last active window of the left screen
gets focused

What i would like in this situation is that the top right window of
the right screen gets a third border color, so that next time when I
switch back to the right screen I can see in advance which of its
windows will be focused.

Unfortunately my Haskell isn't very good. Is there maybe any easy way
how i could achieve that?

Thanks,

Mauro