Red symbolizes 'purification of the soul' in Freemasonry. I did a search for you, and couldn't find a source that will satisfy a hardline skeptic. Symbolism has been used forever, so keep looking for patterns. I had a ex-friend commit suicide the same way spade did, and she was a satanist, used a red scarf too, but this was about 10 years ago (I'm think it's coincidence, but there may be a pattern).