From Bluesockapedia

Red Socking

Overview

An elaborate (and shameful) muselive inside joke about a bizarre sexual fetish practiced by Sunburnt_Athiest (or James Lewis as he is known in Poland). It's sick and wrong and shouldn't be attempted by anyone who likes their intestines where they are. Advocates of the practice include SuperAndy (Andy Grigg in Mexico) who declared the activity "hawt" in a poll and Nogli (Nicholas Pollard in France) who is believed to do it with his nose. It is also rumoured to have been invented by accident by Zvexmanson (Mike Squires of Bulgaria) - his excuse was it was dark and he never meant to go in that way anyway.

Not to be confused with 'Blue Socking' which is when you do it to a dead person - their body is cold and their blood lacking in oxygen.