If you are married, you wear a ring to show that you are not available or looking.
If you are engaged, you wear a ring to show that you are not available or looking.
If you weren’t engaged or married, you were available and looking. There were no “relationships.”
Unfortunately, things are a little more complicated now — needlessly complicated. Thus, some people have been experimenting with new rings that show you are available and looking.

There are also lavender rings to show that you are LGBTQ+++++. Kinda like: “I’m radioactive.” Works for me.
I don’t like the plasticky green look much, but one problem with other ring schemes (including “purity rings”) is that they can be hard to distinguish from regular wedding rings, and subtleties like “it’s on a different finger” are lost in real life.