Headphone cable repair question, wire colors

Hello all,
I'm putting a new 1/8" plug on a pair of Audio Technica M50 headphones for a friend - he removed the old plug before he gave the headphones to me. The wire colors are red, green, and black - but I'm uncertain as to which is which (and searching the internet hasn't turned up a conclusive result)...

My best guess at the moment is:
Tip: black
Ring: red
Sleeve: green
Am I way off? Is there a way to test it before wiring it up?
Let me know - I appreciate it!

Thanks thanks, kfhkh