I'll take the ones not soaked in chemicals...
Here you go: www.popsci.com/scitech/article/2002-07/why-are-some-pistachios-red
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.
Haven't seen pink in ages.
Look ma - no red hands
Red fingertips? No thanks!