Black:
Blue:
Black... that is all
I like Black... but the Blue is different and cool.
If the blue was a little more blue I would say they would be perfect.
Friend of mine has the black. I would definitely say blue.
I say white! lol
BLUE
If they're the same price, blue.
I have the blue, and they're gorgeous, but if the price difference isn't your thing the black M50x are still really really nice.
I could see why someone would like the blue version, it gives off this really classical vibe...but I say black.
If you are looking at getting those, I would suggest looking at the HP100 instead (supposing that you can swing the price).