Given the following XML:
<DATA>
	<FOO cat="BLUE"></FOO>
	<FOO cat="BLUE"></FOO>
	<FOO cat="RED">
		<FOO cat="PINK"></FOO>
		<FOO cat="GREEN"></FOO>
		<FOO cat="BLUE"></FOO>
	</FOO>
	<FOO cat="BLUE"></FOO>
	<FOO cat="YELLOW"></FOO>
	<FOO>on you!</FOO>
</DATA>

This:
<xsl:template match="@* | node()">
  <xsl:copy>
	<xsl:apply-templates select="@*"/>
	<xsl:apply-templates />
  </xsl:copy>
</xsl:template>

<xsl:template match="*[@cat][not(@cat='BLUE')]"/>

Produces:

<DATA>
  <FOO cat="BLUE" /> 
  <FOO cat="BLUE" /> 
  <FOO cat="BLUE" /> 
  <FOO>on you!</FOO> 
</DATA>

I don't want the <FOO>on you!</FOO> match.
However, I don't understand how the root element was picked up, I
figured it would be ignored resulting in no results.