What are you using to modify the Spotify colour please?

Another vote for Obsidian. I use it with the remotely-save plugin via WebDav and Nextcloud - completely self-hosted, I haven’t even made an Obsidian account. Sync conflicts are very rare, I’m using it on iOS and four desktops. While I wish it was OSS, nothing I’ve looked at even comes close to the flexibility of Obsidian. I’m using it for daily notes, habit tracking, task lists, and most recently to write a book.