Hello everyone!
I would like to customize the logo and colors from chirpstack application, someone know if it’s possible ?
Thanks!
it possible if you make own build from source.
if you install Chirpstack from repo - it’s not possible.
How to own build?
Does not work!
It does work, else the GitHub Actions would fail as well which is not the case: https://github.com/brocaar/chirpstack-application-server/actions 
Have you followed these steps? Source - ChirpStack open-source LoRaWAN<sup>®</sup> Network Server
Is branding possible for version 4, and if so, how?
As the project is open-source, you could modify the UI to your needs and create a custom build.