Replace lighten() with variable.

Author: simurai

src/select-menu/select-menu.scss

@@ -3,7 +3,6 @@
 // selector-max-type is needed for body:not(.intent-mouse) to target keyboard only styles.
 // TODO: Introduce an additional .intent-keyboard class
 
-$SelectMenu-border: $border-width $border-style lighten($gray-200, 3%);
 $SelectMenu-max-height: 480px;
 
 // Select Menu
@@ -188,7 +187,7 @@ $SelectMenu-max-height: 480px;
   cursor: pointer;
   background-color: $bg-white;
   border: 0;
-  border-bottom: $SelectMenu-border;
+  border-bottom: $border-width $border-style $border-gray-light;
 
   @include breakpoint(sm) {
     padding-top: $spacer-2;
@@ -270,7 +269,7 @@ $SelectMenu-max-height: 480px;
 // A container used to show different kinds of content. Like a message, a blankslate or the loading animation.
 
 .SelectMenu-message {
-  border-bottom: $SelectMenu-border;
+  border-bottom: $border-width $border-style $border-gray-light;
 }
 
 .SelectMenu-message,
@@ -292,7 +291,7 @@ $SelectMenu-max-height: 480px;
   font-weight: $font-weight-bold;
   color: $text-gray-light;
   background-color: $gray-100;
-  border-bottom: $SelectMenu-border;
+  border-bottom: $border-width $border-style $border-gray-light;
 }
 
 // Footer