XML and CSS

Hi,
I have a question relating to XML and CSS. I have an XML document like the one below and would like to know if there is a way of any kind to make the color of the words the way they are in CSS. That is, “red” would be in color red, “blue” would be in blue etc. I only want four lines of code in the CSS file. I have tried hours on end trying to find a way but to no avail. Any help would be greatly appreciated.
Thanks a million.

Here is the XML file:

<?xml version=“1.0” encoding=“ISO-8859-1” ?>
<?xml-stylesheet type=“text/css” href=“test.css”?>
<a>
<b>Red</b>
<c>
<a>Olive</a>
<b>Blue</b>
<a>
<a>Black</a>
Olive
<b>Blue</b>
<a>Red</a>
<a>Black</a>
</a>
</c>
<b>
<a>Red</a>
<b>Black</b>
</b>
</a>

Here is what I have so far with my CSS file:

a * b{color:blue;}
a,b,a{color:red;}