First of all, this is more of a reminder for myself as to how to change the selected item colour on Ubuntu (12.04). The steps are very simple and are as follows:

  1. To start off, we need to open dconf-editor (Press Alt+F2 and type dconf-editor followed by the enter key).
  2. Navigate to the following path: org > gnome > desktop > interface.
  3. Find the key called "gtk-color-scheme" and set the value to "selected_bg_color:#023C88" replacing the hex code with the value of the colour you wish to use (I used #ccc for light grey).
  4. Done!

If anyone knows of a better/quicker way to do this, please let me know!