What I did was change the cells to a certain width and then make the cells have a background, which is the tabs as a graphic...can be done by creating a class in .css. See my skins site for examples...I have a couple of skins with the navigation as tabs like this one:

http://webgeek-design.com/index.php?act ... oductId=54

For the tabs changing color, that's probably a script of some sort that you can most likely find at places like http://dynamicdrive.com/ where once the page is chosen, it replaces the graphic or the color (however you have it set up..either with a color or a graphic for the cell). Here's a particular script they have that's rather nice http://www.dynamicdrive.com/dynamicindex1/ddtabmenu.htm

I have implemented this script on a custom site that I did for myself one time, works really nice.