Mike,
I am still learning but here is what I have observed and it is purely anecdotage: I find it interesting that most browns, blacks, and purples exhibit a drooping neck when ripe whereas most non-dark (greens and yellows) that I have like Battaglia, Smith, LSU Gold, Golden Celeste swell quite noticeably, become softer to the touch, and most importantly for me, develop the dark sugar spots, i.e., it gets ugly. That's how I know. Other yellows and greens may get hangman's neck but not these.
Thanks Meghan, Frank, Charles, Calvin, Pete, Guiseppe, Mike, Goss, and Ryan.