colorize the output; WHEN can be 'never', 'auto', or 'always' (the
default); more info below
ls is probably configured for
--color=auto, which means it only outputs color if it is directly connected to a terminal. (And not to another command like cut.)
You can use
--color=always but be aware that the whole color stuff works by inserting special characters (escape sequences) which turn color on and off. If you cut in the middle of a colored word you will remove the "stop coloring" sequence and the next line will be colored, too.
ls --color=always|less -RS will do what you want.