More details about the event can be found here:
The event is organised by The League of Extraordinary Red Heads. In the above linked-to article they're described thusly;
"Though the highly visible group assembles suddenly in public spaces, not much is known of the inner workings or its true purpose. It purports to be “a social get-together for those with reddish hair and those who love them,” but some suspect it may be a secret society with plans for world domination."It all seems pretty cool actually.
I really like the way they've used the pumpkin theme. In earlier articles I've speculated that in times gone by the pumpkin was a symbol for redheads. Linking it to both Halloween and the Protestant Reformation. Maybe these guys are tapping into a similar vein. The choice of October 1st seems pretty fitting with that in mind too - the month of Halloween.
Redheads should definitely hijack Halloween :D