I had to edit these files:
/usr/share/themes/Ambiance/gtk-3.0/settings.ini/usr/share/themes/Ambiance/gtk-3.0/gtk.css/usr/share/themes/Ambiance/gtk-2.0/gtkrc
(Addition: for Ubuntu 12.04, it seems youjust have to modify the file:/usr/share/themes/ambiance/gtk-2.0/gtkrc, replacing the tooltip backround and foreground color, with the #000000 and the # f5f5b5 color, respectively)
You require root privileges to edit the files. Usegksudo gedit
To edit them.
Searchtooltip
In these files and you'll find the color definitions for the foreground and the background. I use#000000
As foreground and#f5f5b5
As background and now the tooltips in all applications are again readable. After changing the color values simply switch to some other theme and then back to ambiance and the tooltip color is now fixed.
VI/usr/share/themes/ambiance/gtk-2.0/gtkrc
Tooltip_fg_color: #000000
Tooltip_bg_color: # f5feb5 or # f2edbc
Here is the result:
Reference recommendations:
How to change tooltip background color in unity?
Ubuntu eclipse changes the background and font color of the prompt box
Change the color of the prompt panel in Ubuntu (12.04)