What you are after is called a UI mod (UI = user interface).
There are but two at MTS2:
http://modthesims2.com/browse.php?tag=interfaceHave seen others out there elsewhere in the past (but not all that many). It is an above basic level procedure to change the UI color, so be sure to back up your files first. Almost surely also critical is to use a UI mod that matches the EPs you have installed.