_sass: Define module-date-color variable

_sass/custom/module.scss

@@ -10,7 +10,8 @@
   @extend .card-body;
 
   .module-date {
-    @extend .label, .label-purple, .fw-700;
+    @extend .label, .fw-700;
+    background-color: $module-date-color;
   }
 
   span.module-date {

_sass/custom/variables.scss

@@ -17,5 +17,6 @@ $media-queries: (
 
 // Components
 $box-shadow: 0 1px 3px rgba(0, 0, 0, 0.07), 0 4px 14px rgba(0, 0, 0, 0.05);
+$module-date-color: $link-color;
 $schedule-day-min-width: 9rem;
 $staffer-image-size: 80px;