If you need to alternate between two colors, you can use this idiom:
<tr>
<xsl:choose>
<xsl:when test='position() mod 2 = 0'>
<xsl:attribute name='BGCOLOR'>white</xsl:attribute>
</xsl:when>
<xsl:otherwise>
<xsl:attribute name='BGCOLOR'>gray</xsl:attribute>
</xsl:otherwise>
</xsl:choose>
<td> <!-- stuff for columns --> </td>
</tr>
(shamelessly stolen from: Khun Yee Fung. "XSLT: Working with XML and HTML")
If it is not what you want, then
you should tell us more about your requirements - what exactly means "change color of rows dynamically"?
[This message has been edited by Mapraputa Is (edited July 08, 2001).]