Downstream report: https://bugzilla.redhat.com/show_bug.cgi?id=1038556 When using the 'saturation' slider, the hue seems to be changed instead of saturation...
This was removed in xfdesktop 4.11 as a design change decision: https://wiki.xfce.org/design/xfdesktop/settings Drop the brightness and saturation meter (xfdesktop != image-editor) But I'll leave the bug open in the event someone wants to fix it for 4.10.
Now that 4.12 has been released, we can assume that this particular bug will probably not get fixed.