Since I am not blonde, can I reply to this post without being accused of being a blondeist? Or is the term unacceptable? Perhaps I should say people of light coloured hair persuassion instead? Anyway, back to reality and to the topic.
Yes, this has been covered before
here.
To clarify:
Red - You are invisible. You'll see this next to your own name if you are invisible. Mods will also see you online, and they will see red next to you when you are online and in invisible mode. Everybody else will see you as offline (grey)
Grey (not blue) - This user is offline, or they are online but invisible and you don't know it.
Green - This user is online
Invisible users also appear with an * next to their name in the userlist. You'll see this next to your own name if invisible, or mods will see them next to invisible users who are online. Hope that's easier to understand.