Rainbow Penny?

I have five or six BIVs similar to yours Ken. CC is probably correct, but that artificial coloring was probably unintentional. We know of some ways to induce such colors but we do not know of all the ways they are created. I believe most of these type of coins were colored via their environment. Regardless of this, since I don't usually pay for my toned coins and have no intention of selling my toned collection, it really does not matter where or how they were toned. Besides I believe any naturally toned coin can be recreated by a savvy con artist.

I believe if you put clear tape on penny it makes color tone. I going to try this. I'm not 100% sure.

The 1945 looks like someone put some gun bluing on the coin. Thus the color.