wayvr/uidev/assets/gui/wlx_theme.xml

<layout>
  <!-- TODO: deprecate this in favor of theme.xml -->
  <theme>
    <var key="color_bg" value="#24273a" />
    <var key="color_bg_active" value="#44475a" />
    <var key="text_color" value="#dddddd" />
  </theme>
</layout>