Found this in a roll tonight. It has yellow and blue toning, but the picture doesn't do a great job of capturing the blue.
What year is this coin? Yea, its amazing the toning I'm seeing in some of my more recent American coins made from steel (or perhaps it is nickel), which include some of the newer 5 cents, (yellowing like yours), and the state quarters.(light brown/tea coloured staining). I just love the look and hope it continues. Someone in another thread mentioned that he heard that there was a fine layer of oil on the state quarters that was causing this, but no mention of the 5 cent pieces. I can say that none of my Canadian coins which I am assuming is made from the same steel material has done this what so ever, and i got alot of em, and they are stored in exactly the same manner.
nice golden hue. I've seen newer ones that way after being in those little brown envelopes for a couple of years.