Been trying to figure out the same thing. Basically IE8 doesn’t redraw the pseudo elements unless you make a change to the content. So I’ve modified your example here (just CSS): http://jsfiddle.net/lnrb0b/VWhv9/. I’ve added width:0 and overflow:hidden to the pseudo elements and then added content:"x" to each colour option where x is an incrementing number of spaces.
It works for me; hope it helps you!