Well, that's just it. He technically is not a strain. A strain is a guppy with a set pattern, color and tail shape that can be bred back to a member of the same strain with the resulting offspring exhibiting the exact defining characteristics as the parents. This can be done again and again and always produce offspring of the same strain. For example, if you have a male blue veiltail guppy and breed it back to a female blue veiltail, all the offspring will have all the characteristic of the parents without exception, and every one will be a blue veiltail guppy. Furthermore, if you breed any of these fish to another blue veiltail from a different source, the offspring will always be a blue veiltail guppy.He no a fry anymore His momma was just a regular guppie strain colour, with yellow, black and blueish/whitish. I do no know what strain he is /:
Now if you mated a male blue veiltail with a female red veiltail, the resulting offspring wouldn't be either strain. These offspring wouldn't be a strain at all. The offspring would be mongrels with genetic characteristics of both parents. The offspring may exhibit traits of the blue veiltail, the red veiltail, some mix of the two or maybe different characteristics all together. Since the two strains were mixed their offspring and any further generations are not any strain.
Since you combined not only two different strains but also hybridized two species, your fish technically isn't any strain, but rather shows blond coloration with the swordtail trait. These are characteristics that it shares with true strains, but you didn't get it from mating two members of the same strain so your fish doesn't belong to any strain.
Incidentally, most of the domestic strains available today were created by hybridizing closely related species. Swordtail and platy strains were created by hybridizing Xiphophorus helleri, X. maculatus and X. variatus, and probably others as well to a lesser extent. Mollies by hybridizing Poecilia sphenops, P. latipinna and P. velifera, again as well as others to a lesser degree. I'm not aware of any definite hybrids used to create guppy strains. But 60 or 80 years ago a lot of the species we know today, such as Endler's livebearers, red swamp guppies and others weren't known in the hobby as separate species and probably contributed to domestic strains as well as plain old guppies. I have a copy of Exotic Aquarium Fishes by William T. Innes, circa the early to mid-1960s, that discusses the variation of the guppy throughout it's range. A lot of the areas it references as having guppies actually are now known to not to have true guppies Poecilia reticulata, but closely related species instead.
I have greatly simplified things here, and I don't even know how offspring from these two strains would appear, which traits would be dominant, if there are recessive genes that would be expressed, etc. Creating a new strain takes a lot of discipline and recordkeeping. Here is a link about How to Breed Perfect Guppies that serves as a good introduction on the process. I know there are a lot of other articles and sources out there which can help more.