you know, the scrollbar in the right side of the screen

Nope!

the scroll bar is clientside as part of the browser, PHP runs serverside.

If you are wanting to do it with strictly PHP then it can be done, but with alot of unnecessary coding. You would have to use a postback or simulated one, then you would have to manipulate the css stylesheet with PHP to change the look. A more straight forward and seemless aproach would be to use some AJAX and javascript to achieve what you are wanting.

Dustin, dude, you confused me. To change the scrollbar shown by default in a browser, you have only 2 options: CSS or a browser plugin. CSS is much easier, of course.

Sorry to confuse you I don't think I was clear enough. Lets say you have a button or buttons to change the color and a hidden input box with value 1 in a form. Now when one is clicked you can submit the page to its self. At the top of the page is where the code will go. First you will check to see if the hidden input box value equals 1. This just test to see if this is a postback of a sort. If the value equals 1 then you will need to use php to open the stylesheet and edit it to change the color of the scrollbar depending on what color was selected. You then close the file in php and then do a redirect to the pages self. This will now show the updated page with the updated stylesheet, therefor, showing the new scrollbar color. Now I didn't say it was elegant, but it can be done.

You could just as easily change it without reloading the page using JavaScript. Actually, it would be much easier.

Oh, you were cracking a joke. In essence saying that it's pure CSS, but you can choose to update the CSS via Javascript or PHP. See, I'm just too serious to get humor.

I take it your not so confused now