Some types of oven cleaner will strip anodizing. Other cleaning products containing oxylic acid (like Barkeepers Friend) will also work, but may require a huge amount of effort. If your time has any value at all, you'll be better off just buying silver chainrings.

Also note that even if you are successful, you'll be left with a bare aluminum surface that, even if polished, will tend to develop a cloudy, blotchy appearance as it oxidizes and passivates. It's unlikely to match the appearance of the clear anodized silver parts on your bike for very long.