I'm not sure I understand what you mean, but I define my rxvt-unicode colour scheme using options in
~/.Xdefaults.
Here is a great site for trying out colour schemes (it uses .Xresources but the syntax is the same):
http://terminal.sexy/
If you mean the output of `ls` then you probably have an alias in .bashrc or /etc/bash.bashrc
Code:
alias ls='ls --color=auto'
If you remove this, it will output without the colours.