No-one, I believe is the answer to this thread's question. This first time I saw that photo I thought it looked like gold, not blood, and still do. Look at the background ... those are the carved walls of Akator. Mutt's face is one of awe, as if looking at something that suspends his belief. This would also tie in with the City Of Gold legend, that being the 'aliens' brought the magic of alchemy to Earth with them and at some point Mutt stumbles across a 'gold making device' in Akator and tests it out by dipping his knife into it. This would also explain the very definitive, straight line between the silver of the regular blade and the transformed tip (which is gold).