(defcustom list-colors-sort nil
"Color sort order for `list-colors-display'.
-`nil' means default implementation-dependent order (defined in `x-colors').
+nil means default implementation-dependent order (defined in `x-colors').
`name' sorts by color name.
`rgb' sorts by red, green, blue components.
`(rgb-dist . COLOR)' sorts by the RGB distance to the specified color.