I've always thought the darker blue was for music videos since it's a combination of the audio color and the video color....like music videos are a combination of music and video. I don't know for sure, that was just always what I assumed it was.
I'd also be interested to learn what it actually is if that's not the right answer.
I forgot my forum password and have been too busy/lazy to rest it until now.
but that answer seems logical, and looks like it is about the same ratio as the size my music videos take up.
its strange they haven't documented that
thanks everyone for the prompt answers <3