Is it possible to alternate row colors for collection_select



I have something as such:

collection_select(:obj, :types, @types, :id, :name, {}, {:multiple =>
true, :size => 4})

and I want the row colors to alternate. This is easy to do when manually
building the options tags (as you just add a class name for every other
tag), but I cant figure out how to do it the rails way

Any suggestions?