Unusual color from leaking battery. What happened?

Question

I was removing old batteries from a camera the other day. One of the batteries had leaked something very bright blue. I have seen batteries leak before and typically the colors look a bit like a corroded penny - pale green to white. This time it was a beautiful bright blue; what was it? I initially thought this could have been the metal making the connection was corroding as opposed to the color of the contents of the battery. However, I am not so sure about that.

Note: I believe they were double or triple A batteries and not LiION.

Answer 1

It is, as you suspected, likely a copper corrosion product. Copper compounds are usually blue or green, and are used as pigments. Malachite, http://en.wikipedia.org/wiki/Malachite, is one of the likely corrosion products of an alkaline battery and copper terminals.

BTW, you may need to rinse the battery compartment and use a file to remove the corrosion from the contacts to make connection.