If you are on CF9, the ternary operator will work quite nicely.
I'm actually in CF9 on our development server but CF8 in prod and test still where I need to set this up. That does sound interesting and I'll have to keep that in mind for future development. Is there a way in CF8 to do this?
<tr bgcolor=<cfif something>colour1<cfelse>colour2</cfif>
<tr valign="top" bgcolor="#iif(condition goes here, de('colour1'), de(colour2))#">
Are you creating a new row in your table for each date between your range and you just want to highlight the rows that match your "special" dates? I think a ListFind() would work well here, unless you have a bazillion "special" dates:
<!--- build special list (probably this will come from a DB Query + ValueList() call--->
<cfset sMyDatesList = "11/5/2011,11/10/2011,11/12/2011">
<!--- inside your loop --->
<tr <cfif ListFind(sMyDatesList, DateFormat(dtIncrementingDateVar, "m/d/yyyy")>class="special_date_class"</cfif>>