iranians, color of the hair

have been the Iranians tribes having blonde hairs?
The question has no racist underground but is intended to clarify a feature
about a certain tribe considered to be of Iranian origin. I mean here the
folk of "Agathyrses" which are described as being blonde but they are
considered by most shcolars as being of Iranian origin.I wonder if there are
some ancient descriptions which speak about the Iranic tribes as being
blonde.

Alex