Top right corner of this page -> My settings -> Carbon.
Thanks, but it was already on that. It's gray, but I used to have it kind of a midnight blue. It was either AF or BE that had the option, but I don't see that option anymore.
Didn't know there was such an option. When you find it, do let me know where it is.
Not for myself (I use the light background --- aluminum --- and the gold/green logo and the v1 favicon), but just for general knowledge (in case they ever ask about it on Jeopardy).