Using any theme other than the default means that it's just about impossible to post a message without logging in...

My web browser is configured to ignore colors specified by websites, so the difference is less obvious. I still almost always remember to log in, because if you're not logged in there's a login form on the page, but I've been known to forget on occasion.

And no, I'm not going to subject myself to the arbitrary aesthetic whims of every website I ever visit just so I'll notice more easily if I'm not logged into Perlmonks. I haven't surfed the web with site-specified colors enabled (well, not on anything resembling a regular basis at any rate) since approximately 1998. Too many webmasters have terrible tastes in colors.