You just need the latest Pi OS Bookworm release.
https://www.howtogeek.com/raspberry-pi-os-finally-has-a-dark-mode/?utm_source=dlvr.it&utm_medium=blogger
https://www.howtogeek.com/raspberry-pi-os-finally-has-a-dark-mode/?utm_source=dlvr.it&utm_medium=blogger