I’ve built a handful (lol) of gloves over the years. Heat, chemical patinas, or time. Those are your options. Time is self explanatory and you can Google “chemical patina copper” for info on that.
I like using heat, usually mapp gas. How long you heat it and which side you heat from will affect the tone of the copper. The red fingertips come from a mix of the brazing flux, heating from below, and quenching.