Most likely, both the quote and the alias to the ls
command come from the user's shell configuration files. As mentioned the minus sign as first argument of su preserve the user's own environment, that is switching this way it executes all the statement inside the configuration files placed in the user's home directory.
The quote comes from the fortune
command. You may check where it's placed in your hidden files under your home directory, together with the alias definition, e.g
nado$ grep -E 'fortune|alias *ls' $HOME/.*
You may also check the value of the environment variable $LS_OPTIONS (where defined) to see if the --color option of ls appears.
The question now is: which configuration files are sourced and in which situation (login shell, interactive non-login shell, switching user w/ or w/o minus sign and so on)? You can try to answer by reading http://www.gnu.org/software/bash/man...#Invoking-Bash
and the next chapter http://www.gnu.org/software/bash/man...-Startup-Files
(assuming you're using bash as default shell) plus
Since there are multiple options depending on the presence/absence of some files, you have to investigate your system and the users' set-up directly on your machine. Hope this helps.