So unfortunately I don't have the penny I am talking about so non pictures, but I can explain it. So I found a penny long time ago that has a very strong rainbow like hue, kinda like a static white noise look to it. Every time I put it in the light (especially sunlight) the rainbow colors popped out like it's gay pride haha and the coin looked brand spanking new. Not a color change in the copper behind all the hue. What could cause this in a penny?
I have found Cents in the streets of the City that look like your description.. It's usually dry urine toning... Seriously