Changing the color of window bars

[Pietro Battiston <ml pietrobattiston it>]

Hello everybody,

I'm a bit confused by where the colors of the window bars (decorations)
are determined.

I would really really like to have the active window with a different
color from non-active ones (currently, non-active ones are only blurred
and a bit more opaque). Any color would be fine (while as it is now I
spend a significant time every time I want to understand on which
monitor I am writing).

Unfortunately, I didn't find anything related in gnome-shell.css.

After some search I have found this email:
https://mail.gnome.org/archives/gnome-shell-list/2011-May/msg00480.html
suggesting that this is handled by the metacity theme, in my case
Metabox. However, changing it (with gnome-tweak-tool) does change the
appearance... except for the color!

Vice-versa, if I run "metacity-theme-viewer Metabox", I see window
borders are blue! So where does the grey color come from?

I looked a bit around dconf and gconf apparently related keys, but with
no success (if I understood correctly, the value of the
"gtk-color-palette" key is now ignored).

Thanks a lot for any help,

Pietro

P.S: I'm writing from a gnome-shell 3.8.4 (debian testing), but some
videos I saw of 3.10 seem to suggest my issue would not be solved by
updating.