diff --git a/src/utility.lisp b/src/utility.lisp
index 8fbaac3..7c8b302 100644
--- a/src/utility.lisp
+++ b/src/utility.lisp
@@ -53,39 +53,39 @@
 
 (in-package :cl-sbt/utility)
 
-(defparameter *colors* '(:primary :secondary :success :danger :warning :info :light :dark :body :muted :white :transparent))
+(defparameter *colors* '("primary" "secondary" "success" "danger" "warning" "info" "light" "dark" "body" "muted" "white" "transparent"))
 
 (defun string-clean (str)
   (string-trim " " (string-downcase str)))
 
-(defun background (&key (color :primary) (gradient nil))
+(defun background (&key (color "primary") (gradient nil))
   "Generates a Bootstrap background class.
 
-COLOR: Specifies the color, should be :primary, :secondary, :success,
-:danger, :warning, :info, :light, :dark, :body, :muted, :white, :transparent,
+COLOR: Specifies the color, should be 'primary', 'secondary', 'success',
+'danger', 'warning', 'info', 'light', 'dark', 'body', 'muted', 'white', 'transparent',
 or nil (default color).
 
-GRADIENT: Specifies if the background should have a gradient, should be :t or
-:nil. If :t, it will add a 'bg-gradient' to the class string.
+GRADIENT: Specifies if the background should have a gradient, should be t or
+nil. If t, it will add a 'bg-gradient' to the class string.
 
 Example 1:
-  (background :color :primary)
+  (background :color \"primary\")
   ; This will generate a string 'bg-primary'
 
 Example 2:
-  (background :color :danger :gradient :t)
+  (background :color \"danger\" :gradient t)
   ; This will generate a string 'bg-danger bg-gradient'
 
 Example 3:
-  (background :color :light)
+  (background :color \"light\")
   ; This will generate a string 'bg-light'
 
 Example 4:
-  (background :color :dark :gradient :t)
+  (background :color \"dark\" :gradient t)
   ; This will generate a string 'bg-dark bg-gradient'"
-  (assert (member color *colors*) nil "Color can't be nil")
+  (assert (member color *colors* :test #'string=) nil "Color can't be nil")
   (let ((color-str (format nil "bg-~a" color))
-        (gradient-str (if (eq gradient :t) " bg-gradient" "")))
+        (gradient-str (if (null gradient) "" " bg-gradient")))
     (string-clean (concatenate 'string color-str gradient-str))))
 
 (defun color (&key (text nil) (background nil) (emphasis nil) (body nil))
diff --git a/tests/utility.lisp b/tests/utility.lisp
index af7f86a..3ad71e7 100644
--- a/tests/utility.lisp
+++ b/tests/utility.lisp
@@ -18,17 +18,17 @@
 
 (deftest test-background-color
   (testing "Generates correct background class with color"
-    (ok (string= (background :color :primary) "bg-primary"))
-    (ok (string= (background :color :danger) "bg-danger"))
-    (ok (string= (background :color :light) "bg-light"))
-    (ok (string= (background :color :dark) "bg-dark"))))
+    (ok (string= (background :color "primary") "bg-primary"))
+    (ok (string= (background :color "danger") "bg-danger"))
+    (ok (string= (background :color "light") "bg-light"))
+    (ok (string= (background :color "dark") "bg-dark"))))
 
 (deftest test-background-gradient
   (testing "Generates correct background class with gradient"
-    (ok (string= (background :color :primary :gradient :t) "bg-primary bg-gradient"))
-    (ok (string= (background :color :danger :gradient :t) "bg-danger bg-gradient"))
-    (ok (string= (background :color :light :gradient :t) "bg-light bg-gradient"))
-    (ok (string= (background :color :dark :gradient :t) "bg-dark bg-gradient"))))
+    (ok (string= (background :color "primary" :gradient t) "bg-primary bg-gradient"))
+    (ok (string= (background :color "danger" :gradient t) "bg-danger bg-gradient"))
+    (ok (string= (background :color "light" :gradient t) "bg-light bg-gradient"))
+    (ok (string= (background :color "dark" :gradient t) "bg-dark bg-gradient"))))
 
 (deftest test-background-no-arguments
   (testing "Generates correct background class with no arguments"