Quote from Ubuntu Forums:
Problem with pink borders occurs, when you have too new version of Adwaita installed on your system. In order to have always up to date version of Adwaita, I made symlinks from /usr/share/themes/Adwaita contents (without gtk-2.0 directory) to ~/.themes/Advaivium.
So, go to
/usr/share/themes/Adwaita directory and make symlinks (right click, Make Link) of all content except
gtk-2.0 directory and copy all symlinks to
yourusername is your username on computer).