The attached contribution when added to slime setup enables ANSI colors in slime output.

How to use:

Add 'slime-repl-ansi-color to (slime-setup) call, like this

(slime-setup '(slime-fancy slime-repl-ansi-color))

How to test:

;; Under SBCL (sb-ext:run-program "/bin/ls" '("-l" "--color=yes" "..") :output *standard-output*)

Example of how it looks: http://i.imgur.com/6Cbef.png