adding css class to option tags generated by collection_select?

I know that passing :class => "foo" in the html_options argumnet to
collection_select will generate a select tag with a class assigned to
it (e.g., <select class="foo">)...but I really need my options tags to
have a class of their own which I can determine using live data (e.g.,
style the options in different colors determined by state at
runtime).

I'm doing this manually now but am hoping there's a more Rails way to
do this.