If you don’t like the default Empathy message box theme or if you want to try something else, you might want to try Ambiance the Adium Message Style Theme for Empathy. You can also use the theme for Emesene and Pidgin. I don’t use Emesene/Pidgin so i only made this guide for installing the Ambiance Adium theme on Empathy.
To install the theme you first need to make the adium and the message-styles folders in your .local/share folder. To do this open a terminal window (press Ctrl+Alt+T) and copy+paste the following line:
mkdir .local/share/adium/ && mkdir .local/share/adium/message-styles/
To download, extract and move the Ambiance Adium theme to the folders you just made copy+paste the following lines:
cd ~/Downloads/
wget http://gnome-look.org/CONTENT/content-files/146855-Ambiance.AdiumMessageStyle-1.8.tar.gz
tar -xzvf 146855-Ambiance.AdiumMessageStyle-1.8.tar.gz
mv Ambiance.AdiumMessageStyle/ ~/.local/share/adium/message-styles/
When done you can close the terminal window and to use the Ambiance Adium message style click on the SuperKey button and search for: empathy
To enable the theme follow these steps:
In the Empathy menu Select Preferences
Select the Themes tab
Click on the Chat Theme button
Select Ambiance
There are some variants available under the Variant button. Click on it and select them to get a preview of the variant and select the variant you like.