This is what I found in unpacked Mobi...
Code:
<font color="blue"><a href="http://www.LUNA-Books.com">www.LUNA-Books.com</a></font>
So yes, the publisher is forcing the links to be blue.
Of course, the reading software could be using blue as a default when no color as specified for a link. So even if there is no color specified, you might have to specify a color to get the links not to be blue.