The blue model is one where all the components are made outside of China (Indonesia or Malaysia, not sure) and then sent to the USA for construction. Its a USA made version to allow the defence industry to use them without a risk of having other countries get in the electronics.
The orange and Yellow are built with F7 processors. One has 2 meg of memory and the other has 4 Meg of memory. The Black has 1 Meg of memory and the last time I checked, Ardupilot FW is about 850Kb in size. The Black also uses an F4 processor (and only around a quarter of that processing is used). Chinese copies will be marketing their “faster processor” so these allow Cubes to sound relevant even though they are currently a bit overkill.
The colour red is saved for a super computer version that does not yet exist