xslt 1.0 - display only one distinct value in a table cell as part of a multi-column table and alternate colors

xslt 1.0 - display only one distinct value in a table cell as part of a
multi-column table and alternate colors

I've got an xml file that has some data that is being output in a table
split into two columns (effectively). This is the XML
<structuredBody>
<component>
<section>
<templateId root="2.16.840.1.113883.10.20.22.2.3.1" />
<entry>
<organizer>
<component>
<observation>
<code displayName="TIBC" />
<effectiveTime value="8/29/2013 12:00:00 AM" />
<value value="39" />
<referenceRange>
<observationRange>
<text />
</observationRange>
</referenceRange>
</observation>
</component>
</organizer>
</entry>
<entry>
<organizer>
<component>
<observation>
<code displayName="TSAT" />
<effectiveTime value="8/29/2013 12:00:00 AM" />
<value value="25" />
<referenceRange>
<observationRange>
<text />
</observationRange>
</referenceRange>
</observation>
</component>
</organizer>
</entry>
<entry>
<organizer>
<component>
<observation>
<code displayName="Albumin" />
<effectiveTime value="9/5/2013 12:00:00 AM" />
<value value="46" />
<referenceRange>
<observationRange>
<text />
</observationRange>
</referenceRange>
</observation>
</component>
</organizer>
</entry>
<entry>
<organizer>
<component>
<observation>
<code displayName="ALT" />
<effectiveTime value="9/5/2013 12:00:00 AM" />
<value value="48" />
<referenceRange>
<observationRange>
<text>21-72</text>
</observationRange>
</referenceRange>
</observation>
</component>
</organizer>
</entry>
<entry>
<organizer>
<component>
<observation>
<code displayName="Bicarbonate" />
<effectiveTime value="9/5/2013 12:00:00 AM" />
<value value="69" />
<referenceRange>
<observationRange>
<text />
</observationRange>
</referenceRange>
</observation>
</component>
</organizer>
</entry>
</section>
</component>
<component>
<section>
<...>
</section>
</component>
<component>
<section>
<...>
</section>
</component>
</structuredBody>
I've got the output formatted so that the resulting entry nodes run down
and then over so that the output is:
<table>
<tr>
<td>8/29/2013</td>
<td>TIBC</td>
<td>39</td>
<td></td>
<td>9/5/2013</td>
<td>ALT</td>
<td>48</td>
<td>21-72</td>
</tr>
<tr>
<td>8/29/2013</td>
<td>TSAT</td>
<td>25</td>
<td></td>
<td>9/5/2013</td>
<td>Bicarbonate</td>
<td>69</td>
<td></td>
</tr>
<tr>
<td>9/5/2013</td>
<td>Albumin</td>
<td>46</td>
<td></td>
</tr>
</table>
This gives me:
[entry 1] [entry 4]
[entry 2] [entry 5]
[entry 3]
which is what I'm looking for and that's great.
What I can't figure out is how to get the different 4-cell entry sets to
alternate colors as it goes through. I can't use position() because I'm
manipulating it to get the desired output order in the table. If I output
the position to figure out the math, on the left column, it's always "1"
and on the right column it's always "2" so I can't do a position() mod 2 =
1 to set a style attribute.
Secondly, I only want the date value to appear one time and then not
appear until it changes. That would make it such that the output ideally
should look like:
<table>
<tr>
<td>8/29/2013</td>
<td>TIBC</td>
<td>39</td>
<td></td>
<td bgcolor="dcdcdc"></td>
<td bgcolor="dcdcdc">ALT</td>
<td bgcolor="dcdcdc">48</td>
<td bgcolor="dcdcdc">21-72</td>
</tr>
<tr>
<td bgcolor="dcdcdc"></td>
<td bgcolor="dcdcdc">TSAT</td>
<td bgcolor="dcdcdc">25</td>
<td bgcolor="dcdcdc"></td>
<td></td>
<td>Bicarbonate</td>
<td>69</td>
<td></td>
</tr>
<tr>
<td>9/5/2013</td>
<td>Albumin</td>
<td>46</td>
<td></td>
</tr>
</table>
I can't put the bgcolor attribute in the tag because it should alternate
even across the "columns" and not just the entire row.
Thanks for any help. This site has brought my xslt knowledge a long way.
I've only started delving into it in the last month.