I find the yellow text in the green box of a question that has been answered difficult to read. I wouldn't necessarily like to see this changed, but I think an addition to the box to make it more obvious the question was answered would be a definite improvement.
Would it be possible to add at a stylish ribbon through the top-left corner of the box with the Stack Overflow checkmark on it.
Here's roughly my suggestion. (I just threw these together in a few minutes; It can be done much better, I'm sure.)