Summary

Kotoras UFO and cat themed earrings
Red line - Cut
Black line - Engrave

You can paint the cut pieces of earrings with water colors, if you want a more airy effect. If you want to be more detailed, you can use pigmented markers with good coverage and a small tip size.
As someone who has been making jewelry for many years, another tip is to coat your colored earring with varnish. I sometimes use UV epoxy resin, and I dry varnished earrings in a UV nail lamp. You can certainly use a finishing nail polish of different gloss, and also dry in a UV lamp.