This question already has an answer here:
Since the new user interface was put in place, a notification was added so that users would know when there is more then five suggested edits in the edit queue. This icon has always displayed in a lighter orange color (which I do not have a picture of at the moment).
Then today, I was browsing and I noticed the notification was a shade of red?
I'm assuming the different colors mean different things, but is this documented anywhere?