Remember, the truth is out there, as they used to say on the X-Files.
What could be the reason for the seemingly random appearance of distinctly deep-violet squirrels? This article reports on an incident in Pennsylvania (US) and makes mention of earlier sightings in England and in Minnesota (US).
If you read that article you’ll notice (as you can see in the photo to the left), that the coloring is somewhat splotchy.
Of course, there’s a Facebook page for Purple Squirrel now, too.