I know nothing of Bloods but this is how I look at it.
Intergrade - Something that would happen naturally in the wild between species. Different subspecies of the same species that would share territory.
Cross - 2 subspecies of the same genus / species that wouldn't see each other in the wild.
Hybrid - Ball Python x Burm, Carpet x GTP, Kingsnake x Corn etc.
Not sure if this is really right but that's how I have always looked at it.