wayvr/uidev/assets/gui/wlx_theme.xml

<layout>
  <theme>
    <var key="bg_color" value="#24273a" />
    <var key="bg_color_active" value="#44475a" />
    <var key="device_color" value="#666666" />
    <var key="text_color" value="#dddddd" />
  </theme>
</layout>