Perhaps I'm just color-blind, but for me it is impossible to tell the difference between the accepted and not accepted checkmarks next to answers to my questions:
Even when they are right next to each other, the difference between the two is faint. Instead, I have to hover over the checkmark, deducing which state the answer is in based on the hover text.
Would it be possible to make the grey more faded, or the green more green? Perhaps even use a blue checkmark, the same color as used by the "upvote" button?