Barney's hair loss in the color episodes

I can't help but notice in the episodes where Barney appears, especially where Barney holds the Summit meeting at Andy's house, that he is going bald. The courthouse scene after he and Andy came back from Mr. McCabe's involves him messing up his hair and all of a sudden, a bald spot appears. I noticed that when he was in the black and white episode where he was singing in the choir, doing his solo, he bends forward and the hair loss isn't as apparent.