Summary

Red Color - Cut
Black Color - Engrave

After cutting and engraving the earrings on a laser machine, you can play with painting in various colors and make a unique piece of jewelry with your own stamp.
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.