dbuttons should change color when finger down on them, revert to normal color on finger up

I don't think I see a way to have a dbutton visually indicate it's being touched, right?  

Would you consider adding that?  It's feedback I saw on diaspora that a lack of finger-press feedback was frustrating.  

I was thinking of a fill color specified during finger down, which then reverts back to normal fill color after finger up.
