Rated 5 out of 5 stars
There should be a 2nd timer for _visited_ sites.
Say I visit www.inter.net and get cookies from singleklick.net, inter.net and some more.
Now if I get redirected from www.inter.net to pay.3rdpartybank.net, I'd love to see cookies beeing deleted after 10 seconds which came from singleklick.net, but the ones which came from inter.net shouldn't be deleted before a much longer timeout lapses - say 10 minutes. So I can safely pay and return within 10 minutes without having to remember to switch to grey!
Of course the "timer for recently visited sites" should be user customizable with a sane default :-)