Aviz,
First, Welcome to the Board, from NJ.
You have the right idea-if you don't ask, you can't learn nearly as quickly.
Regarding your "why black" question: the SP twin jets (I think thats the formal name) originally came in two colors, all black and all grey.The colors were NOT cosmetic-they were the result of different materials-or different variations on the same material.
The grey fins were much more flexible than the black-and many people felt that they were "too flexible".
SP's early ads stated that the black gave the advantages of the split "propeller" fin, with more of the feel of a "regular"(paddle?) fin-hence an easier adaptation.They also claimed that the greys were the "ultimate" in propeller fin technology-explaining the greater flexibility.
I have a pair of the black-and I love them. While not a major difference in air consumption vs. my USD "Blades", I noticed a major reduction in leg fatigue during 4-dives a day trips.
While I am a warm water recreational diver, the "blacks" seem to be able to do all that a paddle fin can do. (I can't comment on tec uses- no experience there.)
All that said, I have seen ads for the Twin jets in other colors-blue, yellow-and in a full foot model-black,or ???
I'm not sure what the material is- but it could be the same as the original twin blacks.
Hope this is helpful,
Good Luck,
MikeD