This reminds me of this UX Overflow post about the right way to do "Yes, delete it": http://ux.stackexchange.com/questions/49991/should-yes-delete-it-be-red-or-

This reminds me of this UX Overflow post about the right way to do "Yes, delete it": http://ux.stackexchange.com/questions/49991/should-yes-delete-it-be-red-or-green http://ux.stackexchange.com/questions/49991/should-yes-delet... I think a more contrasting approach to color is likely better - maybe you start with a green button, which goes Gray on click, and then fills with brighter green. This will avoid issues with color-blindness, or even just myopia, where people won't really see the subtle color filling in.