Column's Sortable changed table's background color

I've a table which is:

<display:table cellpadding="2" cellspacing="1"
        name="${xxx}" id="xxx"
        styleClass="black11" bgcolor="#b3b3b3" export="true"

and when I add sortable to one of a column,column's title background changes.

<display:column title="Company Name Company Id" sortable="true" sortProperty="companyName">

I mean: before adding sortable="true", background color was grey, after adding that it 开发者_运维知识库changes to kind of blue; how can I stop that changing?

---

You could define that in your CSS, what is the HTML that that piece of outputs?