For example here is simple dataTable code. You can adjust style in CSS or style argument, if you want grey headers.
<p:dataTable id="dataTable" var="car" value="#{tableBean.carsSmall}">
<p:column style="background-color: grey">
<h:outputLabel>row name</h:outputLabel>
</p:column>
<p:column headerText="column name">
</p:column>
<p:column headerText="column name">
</p:column>
<p:column headerText="column name">
</p:column>
</p:dataTable>