struts2-jquery plugin 如何修改主题

[kgd1120]

如题，默认的主题风格不适合系统，想更换主题，但不知道如何处理，struts2-jquery plugin是引用JQuery-UI1.8

  <s:if test="%{theme == 'showcase' || theme == null}">
      <sj:head debug="true" compressed="false" jquerytheme="demo" customBasepath="themes" loadFromGoogle="%{google}" ajaxhistory="%{ajaxhistory}" defaultIndicator="myDefaultIndicator" defaultLoadingText="Please wait ..."/>
  </s:if>
  <s:else>
      <sj:head debug="true" compressed="false" jquerytheme="%{theme}" loadFromGoogle="%{google}" ajaxhistory="%{ajaxhistory}" defaultIndicator="myDefaultIndicator" defaultLoadingText="Please wait ..."/>
  </s:else>

	<div style="background-color: buttonface;">

		<sj:dialog id="mydialog" title="测试 窗口"   dialogClass="background-color: red;"  position="">
     Mauris mauris ante, blandit et, ultrices a, suscipit eget, quam. Integer ut neque. Vivamus nisi metus, molestie vel, gravida in, condimentum sit amet, nunc. Nam a nibh. Donec suscipit eros. Nam mi. Proin viverra leo ut odio. Curabitur malesuada. Vestibulum a velit eu ante scelerisque vulputate.
    </sj:dialog>

	</div>

[/code]

主题目录下面有很多的css，不知道如何改，请教高手。