I have yet to see Blue Diamond in person but the carbon like in the first picture, it have a jet black painted shell.
I do wonder that also but I'm not sure how much more you can improve the painted area.
Year ago, I use to keep Blue rilis and breed mix in some painted fire red to improve the painted red of the head and tails. I was able to get them to be darker but the pattern was the challenging part. Maybe i was working with lower grade shrimps, or just not good enough, the pattern were never as clearly define as these guy (carbon). They were more random. But time will tell, this time around, it's a better starting point than my last attempt.
Plus, I'm sure as they become more available, someone will probably tell us if not already