The XSL below illustrates how to alternate color using the mod operator and setting the style class. This allows to to create a general ledger look.

    <xsl:template match="log/entry">
        <div>
            <xsl:if test="position() mod 2 = 1">
                <xsl:attribute name="class">LogEntryHighlight</xsl:attribute>
            </xsl:if>
            <xsl:if test="position() mod 2 = 0">
                <xsl:attribute name="class">LogEntry</xsl:attribute>
            </xsl:if>
            <xsl:value-of select="."/>
        </div>    
    </xsl:template>