Amanita citrina f. lavendula
See description and discussion at
This beautifully colored specimen of Amanita citrina f. lavendula was found
growing from the ground in a white pine grove late September.  This collection
never saw temperatures below 50 degrees Fahrenheit, which doesn't conform to
the theory that cold temperatures affect coloration.

Michael Kuo, in discussing this species relates the following:

"There is a nomenclatural nightmare surrounding this mushroom, which North
American authors have long treated as "
Amanita citrina," assuming it is the same
as the European species that often bears the same name. However, for
taxonomic reasons the correct name for the European species is actually
Amanita bulbosa var. citrina--and that mushroom is, it turns out, distinct from the
North American mushroom, leaving the taxonomically awkward Amanita citrina f.
lavendula as the best North American name. To complicate matters, Amanita
expert Rod Tulloss (2013) reports preliminary DNA results supporting the idea
that the North American version of "
Amanita citrina" is actually composed of at
least three genetically distinct species, and suggests that we can expect
"nomenclatural and taxonomic changes" in the near future." (And here they are:
Amanita lavendula.)

Amanita citrina f. lavendula at MushroomExpert.Com