if you mean as opposed t the blue color... you don't unless you find a custom theme. if you mean in the classic version just right click your desktop go to properties and go from there..
Get the neowin multi patcher here http://www.llbbl.com/data/nw_uxpatcher.zip (this will patch your computer so you can apply custom themes) and get themes at deviantart.com by going to browse>skins and themes> and under sub category visual styles.
thanks that is what i need thanks alot Edit.: oh and how do i add the skins to it know i dont know how.