From a discussion in the xfce forum ³ re. monitor color profiles support in xfce4-settings
I figured two things:
1. it seems to need to be built with this support ¹
2. it seems to need gnome-color-manager to show-up in the GUI ²
Re. #1, in fc30 it seems the packages wasn't built with this option and would need an
update (I didn't check the spec file but /usr/bin/xfce4-color-settings is missing).
Re. #2, I suppose the package would need to at least recommend gnome-color-manager .
¹
https://git.xfce.org/xfce/xfce4-settings/tree/configure.ac.in#n162
²
https://git.xfce.org/xfce/xfce4-settings/commit/?id=449e9d9a6f4a341d63ff5...
³
https://forum.xfce.org/viewtopic.php?id=13297