Tobigara
Fishaholic
Its all fake my friend. There is no natural living Yellow Oscar or blueberry jack living today. These are dye colored originals like parrots. These farmers bred these kinds of fish to make more money coz of the color and anyone who is uneducated about these things would buy them. So the seller is preying on ppl's stupidly pretty much.
i can't say anything about yellow oscars but blue jd's are found in nature. i don't think you have done any real research. blue jd's are perfectly natural. they are usually killed in nature because they are smaller and less aggressive so they either get killed outright or starve because they can't compete for food.
http/www.geocities.com/jackarthur46/electric_blue.html
I don't think they are any more or less hardy that regular jd's. they do however grow a lot slower than the regulars as IzzyD stated