wayvr/uidev/assets/gui/theme.xml

<layout>
  <theme>
    <var key="menu_dark" value="#0A0A0ACC" />
    <var key="background_dark" value="#0d131acc" />
    <var key="background_light" value="#244179aa" />
    <var key="bottom_panel" value="#141e28" />
  </theme>
</layout>