A bit early for theology, but, you know.
I met Drayton Parslow wandering across the ley, and he showed me his latest pamphlet, "Forsake thy Grievous Sins Which Cry out to Heaven for Vengeance, or Thou Shalt be sent to Perdition for Thine Iniquities". He reckons it will be a great evangelistic tool for the totally unchurched who are well-versed in the King James Version of the Bible.
And there's a passage in the early sections, before all that obsessive interest in the sins of cross-dressing which Drayton always shows. Where it talks about us having the "Mark of Cain". And I asked Drayton what sort of "mark", or "curse", it is. Did he, like some American Baptists, think Cain was given black skin? Or, as some have suggested a horn? The whole "black skin" concept, apart from being vile, also being incoherent, as only Noah's family made it through the Flood (I am reasoning here using the model of the Genesis creation narratives) so you'd expect them all to be pretty much the same skin colour.
Drayton tells me that, since the Bible is silent on the mark itself, any attempt to be specific would be a waste of time. Though he did speculate that maybe Cain just had a distinctive hat.
For myself, I'm looking at this sculpture of Cain (from Wikipedia). And I've got my own theories about what the curse or mark of Cain was.
That's right. He always had a headache.