Gosh that is a weird color for a yolk sac to be. I haven't got a lot of experience but the ones I had that still had the yolk sac attached, the yolk sac was yellow. I almost think your chick has a birth defect, it looks more like organs on the outside or something. Hopefully someone will chime in that knows more than I do. Put a warm wet paper towel all around it except the head to keep it moist and put it in a corner of the incubator where no other chicks will bother it. The paper towel should protect it a little bit too. If it is a yolk sac it will absorb it in a while. I just am not sure that is what it is. Sorry! Keep me updated and good luck! Hatching chicks is stressful!!!!!