Today, the list of questions on the main page suddenly started looking differently. This morning, all questions had the same background. Now, some of them have a greenish background.
It looks like a feature to me. However, I can't figure what the green ones have in common. Also, I didn't reach any special reputation number or flag weight today. So I don't know what it accomplishes, or why it could have been turned on.
I don't mind it, but I am curious. What it is, and why is it there?