No idea how the title connects with the story (and no clue is given), but its poetic turn sure makes it easy to remember. "Demon with a Glass Hand", "Purple Twilight", "O.B.I.T." are standout examples of what came from the short lived Outer Limits series. Like many of the episodes, "Purple" was shot on a limited budget, but manages to give an engaging story - plot line, imagination and effort getting the job done, with a measure of philosophizing dialogue, an OT trademark.
Just plain, simple fun. An alien scientist, with a sinister agenda, arrives on earth, but has an unexpected change of heart after being exposed to a dose of human emotions. Poker face actors Robert Webber, the alien ("I don't live to be liked or disliked."), and Warren Stevens, an obsessed, stressed-out earth scientist ("You serve no purpose, Janet. I have no use for you."), make interesting foils. The girlfriend's role is a bit overemotional (a fate that many of the Outer Limits female leads had to endure), but it's her nature that melts the emotionless, extraterrestrial heart. A nice touch is the three duty-bound, alien policemen who show up to retrieve the now renegade scientist.