diff --git a/ansi.scm b/ansi.scm
index 04fe68a..9c04ad1 100644
--- a/ansi.scm
+++ b/ansi.scm
@@ -32,6 +32,7 @@
 
  (import scheme
 	 (chicken base)
+	 (chicken string)
 	 testing)
 
  ;; Only basic ANSI colors and bold attribute support.
@@ -59,12 +60,30 @@
 	     (loop (cdr lst)
 		   res)))))
 
+ ;; Returns ANSI sequence changing color and/or bold attribute.
  (define (ansi . args)
-   "")
+   (let ((argsl
+	  (map
+	   (lambda (key-color)
+	     (number->string (cdr key-color)))
+	   (filter
+	    identity
+	    (map (lambda (arg) (assq arg colors)) args)))))
+     (if (null? argsl)
+	 ""
+	 (string-append "\x1b["
+			(string-intersperse argsl ";")
+			"m"))))
 
+ ;; Performs ANSI module self-tests.
  (define (ansi-tests!)
    (run-tests
     ansi
+    (test-equal? filter (filter odd? '(1 2 3 4)) '(1 3))
+    (test-equal? filter (filter odd? '(2 4)) '())
+    (test-equal? ansi (ansi #:red) "\x1b[31m")
+    (test-equal? ansi (ansi #:nonsense) "")
+    (test-equal? ansi (ansi #:default) "\x1b[0m")
     ))
 
  )