Umbriel
The built-in Umbriel template generates colors for regular and scratchpad borders, the insertion hint, fullscreen backdrop, and overview tint.
Enable Umbriel under Settings → Templates → Compositors.
Noctalia writes the rendered template to ~/.config/umbriel/noctalia.toml and adds
it to the files array in the [include] section of config.toml. Existing include
entries are preserved. Umbriel reloads both files automatically when they change.