Fix color of compound filter

src/styles/_filtereditor.scss

@@ -2,6 +2,10 @@
   padding: $margin-3;
 }
 
+.maputnik-filter-editor {
+  color: $color-lowgray;
+}
+
 .maputnik-filter-editor-property {
   display: inline-block;
   width: '22%';