Many contaminants in the environment as well as chemicals react to the Copper or Copper plating of Lincoln Cents! You can wash Lincoln Cents with hand soap and it will turn them Magentas to Purples and other colors and many Dishwashing soaps will do the same thing. Leave a Copper cent in the Sunlight and it will tone to some fantastic colors. Unless a Copper cent or other coin is sealed away in a air free, contaminant free holder or protector and kept out of the heat shortly after it's minting, they will likely change colors.
2316
1452
1377
1340
1089
1009
902
841
710
593
588
566
524
512
473
