I always heard that the red ones were Iranian and they were dyed red for some kind of import tax purpose. Don't know if that's true, but with all the embargoes against Iran now it would explain why we don't see the red ones anymore.
Here you go: www.popsci.com/scitech/article/2002-07/why-are-some-pistachios-red
Haven't seen pink in ages.
Red fingertips? No thanks!
Look ma - no red hands
I'll take the ones not soaked in chemicals...