correct theme style at settings page

src/AppDarkTheme.module.css

@@ -1,3 +1,7 @@
+/**
+ * The coloring elements for dark theme
+ */
+
 .backgroundcolor{
     background-color: #141520;
 }
@@ -6,6 +10,10 @@
     color: white;
 }
 
+.subtextcolor{
+    color: #dedad6;
+}
+
 .navitem::after {
     background: white;
 }