for this you need to change the struts themes. Refer the struts documentation. Struts tags are there in struts2core.jar .
The theme templates (simple, xhtml, css_xhtml) can be found in the Struts 2 core jar file. If you expand (extract the files) the Struts 2 core jar file you'll find folders named template.css_xhtml, template.simple, and template.xhtml. Those folders contain the templates for the three default Struts 2 themes. In each folder is a file for each Struts 2 tag. For example if you expand the template.xhtml folder you’ll see the select.ftl file.