A different colour when there's new messages?

Hi there, I think it will be pretty good to have the bottom corner chat box change colour when there's a new message. At this time, I have to open up to check if there's something new there. Not the most interesting of tasks.

Am thinking, maybe when I (moderator) clicks on the chat box, all messages will be marked with a "read" flag. When new messages come in, they will be "unread" and the chat box's color is different. What do you think?