Black colour/Oxidation on silver rings will fade over time. This it true of all black silver jewellery and this is part of the appeal of the design.

Over time oxidation will wear off. In some rings it wears off quickly - in others, it comes off slowly, changing the appearance of the ring. Skin oils, perspiration and soaps will take off the oxidation more quickly.

If the colour has faded to much for your taste then you can re-oxidize at home using eggs.

A good example of how to do it can bee seen in this video here - https://jewelrymakingjournal.com/how-to-oxidize-sterling-silver-and-copper-with-boiled-eggs/