What? It’s a theme generator. You give it a color, it uses Material 3 math, and spits out a theme you can save as a new file to your themes folder (assuming you already set up a themes folder).
https://ktibow.github.io/home-assistant-theme/
What does it look like
Can I get some more selfpromotion
If you know anything about UI design or theme design or the architecture of the HA frontend check out this discussion