--color=auto, which ls is usually mapped to with alias, is a better idea, because it doesn't try to print colours when the output isn't a console -- when the output is redirected to a file, for example. (Otherwise, with --color=yes, you'll probably get lots of ANSI escape sequences.) But maybe --color=yes is what you want, I don't know.
BTW, you can see the currently set aliases by typing "alias". And you can set them like so:
(I made up that output, alias might actually print things slightly differently.)
$ alias gcc='gcc -W -Wall'
gcc='gcc -W -Wall'
alias is built into your shell, which is probably bash. Just in case you're curious.