Reaction between silicone and a US quarter

No.12709458 ViewReplyOriginalReport
Good evening /sci/. I tried making a silicone mold of some small objects like dice, beads, and the pictured quarter (didnt work, lol). Why did it change colors like this? I can only assume some kind of reaction between the silicone and whatever oxides are present on the coin. Open to any and all insight