Guppies and danio's cannot crossbreed, guppies are live bearers and danio's egg scatterers its impossible. I would be worried about using a shop that cannot tell the difference between a guppy and a danio, unless the tank this guy came from just had an old label on it.
I agree with this, the stripes on the lower half look kinda lil what a green cobra cross could turn out like, then theres the black bar on the belly...
looks cool btw, i would breed this if i was you and had the room