Porphyrophobia is a fear of the color purple, a subclass of Chromophobia. Like all other phobias, the original cause of Porphyrophobia traces back to a past traumatic event involving the color purple. This fear could also be due to internal predispositions or thoughts.
Porphyrophobics would be easy to avoid seeing purple due to the rarity of the color, so panic would not occur that readily. Sufferers (especially those who had purple poison ivy rash) may associate purple with poison, readily causing toxiphobia. It is quite possible to get treatment for something like this. A qualified therapist could help dig out the root cause for the fear and take steps towards curing that. A lot of times people can bounce back from this fear with help.