Green Water From Boiled Potatoes

Q:

I took the potatoes out to cool last evening and left water in pot overnight, graniteware. When pouring water out this morning it was a vivid green color!? Typically of course I drain the water and cool in pan  so I’m clueless if time overnight “greened” the water or exactly what happened? Please help!

A:

The potatoes might have been exposed to light which can make the skin have a greenish hue. So this is what I am guessing caused the water to turn green.