Painting with electricity
When you combine an electrolyte solution with different voltages, you can create a rainbow of colors on titanium metal. Here, I'm using a paintbrush dipped in an electrolyte solution and connected to a series of 9V batteries to "paint with electricity".
This site has an amazing explanation and demonstration of the process of anodization: https://thekidshouldseethis.com/post/anodizing-titanium-the-rainbow-metal
And this instructable walks you through how to paint with electricity: https://www.instructables.com/id/Anodize-Titanium/