Kor's soul isn't actually yellow. If you were to operate on Kor (or anyone else for that matter) you wouldn't be able to see his soul inside him. What happens when Snow pulls the souls out of their bodies is that a thin layer of magic wraps itself around the actual soul to protect it outside of the body (an actual soul can't be seen by the naked eye). The shape of this magic shell, like the shape of someone's magic, is determined by multiple factors the magic user has no conscious control over.
And now that the news break is over: NOOOOOO, not Kor! Poor wee Woodstock soul.Uploaded by admin at 03:55 on 02 August