Could be a fire-spider, though it's a tad tough for me to imagine someone hatching out a fire-spider unknowingly and then wholesaling it to a pet store. Could happen I suppose -- I guess one parent could've been an imported fire and the breeder didn't realize it -- but it just seems less likely.

My thought it is that it may be a regular spider who underwent a loss of pigment and became lighter, possibly due to a metabolic stress.

I've had this happen a couple of times now; I ended up selling both animals but have kept track of them both. One, an older female, I think may be an actual "IMG" as she has darkened up significantly since losing her color -- to the point where she is now darker than she was before losing it.

The other, though, was one that I think experienced a metabolic stress that caused him to lose pigment, and that's a little more what your guy reminds me of ... He doesn't look quite as silver/gray as many of them seem to, but it seems that some turn silver and others just get very light ... Without a history I'd think it's a fair hypothesis.

... Though, that doesn't mean that you might not get lucky when you breed her!