fix: demo site color property added twice (DenverCoder1#614)

Author: davidzr

src/demo/js/script.js

@@ -223,6 +223,7 @@ const preview = {
     const option = Array.prototype.find.call(selectElement.options, (o) => o.value === property);
     selectElement.disabled = false;
     option.disabled = false;
+    selectElement.value = option.value;
     // update and exit
     this.update();
   },