Royal Mint (and other) silver proof year set ingots.

I the Royal Miny proof year sets they issue a medallion/ingot in the case along with the coins. In the base metal sets this ingot is copper/bronze, in the silver proof sets it is a silver colour. I have seen the same in othe sets- Pobjoy Mint IOM sets. What I would like to know is , are these silver coloured ingots silver?