turns out that we /do/ use tertiaryAccentColor after all

src/skins/vector/css/_common.scss

@@ -132,6 +132,10 @@ textarea {
     color: $secondary-accent-color;
 }
 
+#mx_theme_tertiaryAccentColor {
+    color: $roomsublist-label-bg-color;
+}
+
 .mx_Dialog_wrapper {
     position: fixed;
     z-index: 4000;

src/skins/vector/css/themes/_dark.scss

@@ -34,7 +34,11 @@ $secondary-accent-color: $primary-bg-color;
 // by overriding the key to something untintable
 // XXX: this is a bit of a hack.
 #mx_theme_secondaryAccentColor {
-    color: #2d2d2e ! important; // deliberately off by one
+    color: #c0ff33 ! important; // deliberately off by one
+}
+
+#mx_theme_tertiaryAccentColor {
+    color: #c0ffee ! important;
 }
 
 // used by RoomDirectory permissions

src/skins/vector/themes/status/css/_status.scss

@@ -90,7 +90,11 @@ $secondary-accent-color: #586C7B;
 // by overriding the key to something untintable
 // XXX: this is a bit of a hack.
 #mx_theme_secondaryAccentColor {
-    color: #586C7C ! important; // deliberately off by one
+    color: #c0ffee ! important;
+}
+
+#mx_theme_tertiaryAccentColor {
+    color: #c0ffee ! important;
 }
 
 // used by RoomDirectory permissions

src/vector/index.html

@@ -27,7 +27,7 @@
         if (match) {
             var title = match[1].charAt(0).toUpperCase() + match[1].slice(1);
         %>
-           <link rel="stylesheet" disabled title="<%= title %>" href="<%= file %>">
+           <link rel="stylesheet" disabled="disabled" title="<%= title %>" href="<%= file %>">
         <% } else { %>
            <link rel="stylesheet" href="<%= file %>">
         <% }
@@ -73,6 +73,6 @@
     </audio>
     <audio id="remoteAudio"/>
     <!-- let CSS themes pass constants to the app -->
-    <div id="mx_theme_accentColor"></div><div id="mx_theme_secondaryAccentColor"/></div>
+    <div id="mx_theme_accentColor"></div><div id="mx_theme_secondaryAccentColor"/></div><div id="mx_theme_tertiaryAccentColor"/></div>
   </body>
 </html>