> It all has to be within the xsl:attribute

But your example stylesheet you posted was did _not_ have the code
inside xsl:attribute.

You can not have element markup inside attribute values in XML (or HTML)
so there is no way to get elements into attribute values, irrespective
of xsl syntax.

> <tr bgcolor="<something-defined-in-my-xml>">

to get that you just want

<tr bgcolor="{@color}">

or any other expression instea dof @color to extract the data from your
input.

David


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list