How I Restored A Tarnished Ring With Nail Varnish. Post 821 in Dress of The Day by Angela Lansbury.
I found an old ring which was tarnished. I wondered what kind of paint I could use on metal which would not be dangerous against my skin. I was in the bathroom and glanced around. Nail varnish. That must be safer on skin than other paints. My first coat of nail varnish created a dark, browny red. But I added a second coat of nail varnish, the effect was bright red. https://nailicy.com/article/how-to-paint-rings-with-clear-nail-polish