I beg to differ, whilst there are a lot of variation in the F1 generation, the dominant traits will show, and therefore it is more likely that although there will be individuals that looks similar to a parent, it will never be the same. In general anyways, of course there are exceptions but with the Red Texans, it's quite obvious when their color is a bit off or whatever.
Maybe down the line, but that's really only if they are continuously breed with one species. To get a hybrid to look like a Green Texas, I'd imagine that it'd be a few generations down the line, assuming practically everytime the one that looks most similar to a Green Texas is well, breed with a Green Texas. So honestly, I see no reason to doubt that the Green Texas shown is pure.
From my experience anyways.
That is where we can disagree because i do not see a pure looking green texas in the pics. What is it i see that is off well a fully colored out tail and fins on a fish this young (at least usually)including a red edge to the top fin (pure green texas or any texas does not have a red edge on their fins but many flowerhorns do) most easily seen in the second pic. Also this is still a small juvi fish and as it grows could still fade. Also petsmart gets their fish from segrest farms and they do not according to an answered email from segrest have green texas (Herichthys carpintis) and petsmart does not take in donation fish. While this all does not mean it is not a green texas I feel it makes it very unlikely that it is.
It is still a very nice fish and one many of us would not think twice about adding to our tanks.