Try
<html>Some black text and <span style="color:red;">some red text</span>.</html>
This should result in
Some black text and some red text.
Now, it should be easy to write some XSLT code that creates this, e.g. use the following snippet:
<xsl:choose>
<xsl:when test="@Change='Omitted'">
<span style="color:red;">red text</span>
</xsl:when>
<xsl:otherwise>black text</xsl:otherwise>
</xsl:choose>
Cheers
Andi