Definitely looks like some kind of purp x flava hybrid. Hard to tell if it's an antho-free clone. The growth point doesn't seem to show any sign of red. But then, there is no antho-free form of S. flava that I know of (var. maxima still has coloration at the growth point). I don't understand Sarracenia genetics all that well, but I would think, since the antho-free is recessive, you would need two antho-free parents to form an antho-free hybrid. I actually have a couple of plants very similar to this, which I don't know the parentage of. They are a little more upright and the lids cover the mouth better. The flowers are nearly identical to flava, so I've always assumed they were flava x (purp x flava). But now that I think of it, there is no red coloration on their pitchers, nor at the growth point.
Anyway, enough of my rambling. Nice plant!