It is not normally something you configure the terminal to do... The terminal is unaware of what it is showing but try this in your shell (if you're using bash, in some other shells you don't export but call setenv or something else):
export CLICOLOR=1
export TERM=xterm-color
You can then use LSCOLORS generator to setup something that you can export using something like:
export LSCOLORS=fxfxcxdxbxegedabagacad
(the above should give you purple directories)
When you're done and satisfied with the result, add the three lines to either your /etc/bashrc or the .bashrc file in your user's home directory.
Edit: Also, in your terminal, make sure the checkbox "Display ANSI colors" (on the "Text" page) is checked.