Hypnosis can result in some pretty remarkable demonstrations of insensitivity to pain, incredible muscular rigidity, the ability to staunch blood flow, the capability of affecting the autonomic nervous system in ways thought to be impossible to control with volition.
Frankly, I have never heard of, nor seen eye color change through hypnosis. Some people claim that dietary changes have changed the pigmentation of their iris, but frankly, this is outside of the purview of my practice or experience. I do see some comments to the right of the page, but I would have to research this on my own. My practice is pretty much focused on the elimination of symptoms and dysfunctional behavior caused by traumas.