I just noticed this:
When you got a notification on Area51, this happens (for me, on firefox 21.0):
The banner feeds in, totally red
After completing the fading effect, the bar turns blue - except for the text. This is the state as can be viewed in the image.
When the window loses focus, the bar turns totally red.
Is this a bug for StackExchange or is my browser doing something wrong? This occurs also with all add-ons and user scripts disabled.
Easily reproducable: logout from Area51 but not from whole SE, then go back to Area51 and reload the page. You get a "Welcome back"-message now, which shows the same bug.