Simple. Environmental Damage. Exposure to sand, soil, dirt and the weather can and will change the color of Clad coins and Nickels.
I metal detect and have found thousands of examples over the years... Here are Nickels.. Bottom row are normal -
Thanks for the reply, Could it be possible that it is painted because it still has detail and it doesn't have a brown color like the picture you showed or is it still damage from being under ground?
dug coins react to ground chemicals and I've found red, green, brown, orange and black. I assume that blue could happen too since I have not dug in all types of soil. Most of those I dug in Germany were blackish with brown highlights. Most of what I dug in Illinois were deep black. Most I've dug or seen from Indiana are a chocolate brown. I wasn't in California very long forty years ago and I don't recall what the nickels looked like.