Nifty little site! If you're looking to make it a little more slick, I would try doing each color change in JS alone and use history.pushState to change the URL. For a cool effect, maybe transition between the two colors since the page isn't refreshing anymore.
I don't find uninteractive random hex generation via URL very handy. If instead of getting a random value when clicking on the text, you allowed me to edit it and show the new value on submit, I'd find it more useful, I think.
Transitions would be cool. More interactivity (drag to change color - this has been done though) would also be very cool.
It's very pretty, though!
Maybe we should join hands - http://randomthing.me/ :)