palemoon-dev/platform/layout/reftests/forms/input/file/style-ref.xul

<?xml version="1.0"?>
<?xml-stylesheet href="style.css" type="text/css"?>
<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
        xmlns:html="http://www.w3.org/1999/xhtml">
  <hbox>
    <html:style>
      .file {
        background-color: blue;
        border: 1px red solid;
        width: 400px;
        padding: 2px;
        margin: 5px;
        display: inline-block;
      }

      .file > label {
        /* color only applies to the label */
        color: white;
      }
    </html:style>
    <html:div class='file'>
      <html:button>Browse&#8230;</html:button><label value="No file selected."/>
    </html:div>
  </hbox>
</window>