I think you can try the following XSL stylesheet with your own XML document...
(you must put "bgcolor" attribute into "td" tag only...)
<!-- ************************************* -->
<?xml version='1.0' encoding='iso-8859-1' ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl

utput method="html" indent="yes" encoding="iso-8859-1" media-type="text/html"/>
<!-- ************************************* -->
<xsl:template match="Atts">
<html>
<head>
</head>
<body>
<xsl:apply-templates/>
</body>
</html>
</xsl:template>
<!-- ************************************* -->
<xsl:template match="Att">
<table>
<xsl:apply-templates select="AttFormats"/>
</table>
</xsl:template>
<!-- ************************************* -->
<xsl:template match="AttFormats">
<xsl:for-each select="AttFormat">
<xsl:variable name="CHOOSE" select="position()"/>
<tr>
<xsl:choose>
<xsl:when test="$CHOOSE mod 2 = 0">
<xsl:element name="td">
<xsl:attribute name="bgcolor">#FFFFFF</xsl:attribute>
<xsl:value-of select="$CHOOSE"/>
</xsl:element>
</xsl:when>
<xsl

therwise>
<xsl:element name="td">
<xsl:attribute name="bgcolor">#AAAAAA</xsl:attribute>
<xsl:value-of select="$CHOOSE"/>
</xsl:element>
</xsl

therwise>
</xsl:choose>
</tr>
</xsl:for-each>
</xsl:template>
<!-- ************************************* -->
</xsl:stylesheet>
i hope it will work fine as you want
Regards
Analogx
(don't hesitate to contact me if you need some help...)