Agree with esshup, the blackness (am I allowed to say this in 2021?) in the bass you used to see probably isn't specific to a certain species or strain, it had to do with the water in which they lived. In muddy/turbid water, they turn almost white, and in clear water, they get very dark.

What you want are most likely F1 bass (see Heppy's reply above), which are a cross between a Florida strain and Northern strain LMB. Due to being a hybrid (though, not a true hybrid), they do experience what they call "hybrid vigor" which would explain their hard-fighting nature that you described.

"In the age of information, ignorance is a choice." - Donny Miller