default checkbox color to positive color

Author: Adam Bradley

scss/_variables.scss

@@ -479,8 +479,8 @@ $checkbox-off-border-royal:       $royal !default;
 $checkbox-on-bg-royal:            $royal !default;
 $checkbox-off-border-dark:        $dark !default;
 $checkbox-on-bg-dark:             $dark !default;
-$checkbox-off-border-default:     $button-stable-border !default;
-$checkbox-on-bg-default:          $button-stable-border !default;
+$checkbox-off-border-default:     $positive !default;
+$checkbox-on-bg-default:          $positive !default;
 
 
 $checkbox-check-width:            3px !default;