I think the Black is meant to be a small modular, cargo carrying fighting ship( Pirate ship if that's what you want it to be).
I think the thing with Drake and most other makers is they make a ship or it's variant with an intent or role in mind, but that does not limit what the ship can be.
I think the Black is meant to be a fighter that can carry cargo, you can take that cargo from others or just use it for legal means. But it is kind of the base model. It will fly and be able to do some jobs out of the box but it's kind of a blank canvas for you to make what you want of it.
You could probably even make a exploration ship out of it if you wanted. Put in a nice jump drive, some long range scanners, extra fuel tanks, more fuel friendly engines.
The Red I think is really meant for S&R (it also shows the versatility of the Cutlass you can make what you want of it within some limits)
The Blue I think is really meant to be a tougher better armed Bounty Hunting ship.(tougher and better armed than say an Avenger). Now could you use the Blue to kidnap people or remove the holding cells and use it to take cargo from other weaker ships? Sure. But I think it kinda goes to show that there are upgrades and modifications you can make to the Cutlass and it can serve another role.
It's kinda like how the 350R is sold as a racing ship but it is hinted that the UEE has a whole squad of them kitted out for Spec Ops.