I download Firefox Developer Edition, unpack, run and see "white" GUI.
Can I make look stable Firefox like Developer Edition - with dark GUI?
I am at Xubuntu 14.10.
Visit about:config
Double click on browser.devedition.theme.enabled preference to change its value to ‘true’.
Next, set devtools.theme preference value to either ‘dark’ or ‘light’, no restart is required.
This might be from an earlier version i'm not sure. But its worth a try i guess.