fix #510: [Bug] Styling of the icon labels and overflow icon is not correct

src/scss/menu.scss

@@ -287,14 +287,6 @@
   }
 }
 
-.cm-standardmenu {
-  visibility: hidden;
-
-  &.show {
-    visibility: visible;
-  }
-}
-
 .cm-always-displayed {
   body {
     width: calc(100% - 50px) !important;
@@ -426,11 +418,25 @@
 $header-icon-size: 20px;
 
 .cm-standardmenu {
+  visibility: hidden;
   width: 100%;
   display: flex;
   flex-shrink: 1;
   flex-wrap: wrap;
 
+  &.show {
+    visibility: visible;
+  }
+
+  svg {
+    color: var(--color-background-plain-text) !important;
+  }
+
+  .app-menu-entry--label {
+    color: var(--color-background-plain-text) !important;
+    filter: var(--background-image-invert-if-bright, var(--primary-invert-if-bright)) !important;
+  }
+
   .app-menu-main {
     display: flex;
     flex-wrap: nowrap;