Cheers Egg!

This is the most versatile I can get for you.

In Xara, create your text with a white text colour, add its link and place over your black background. You can mix and match these colours.

Add a Placeholder object with the following HTML Code (body):
<style>

a:link {
color: White;
text-decoration: none;
border-bottom: 1px solid;
border-bottom-color: LightYellow;
}
a:visited {
color: Bisque;
border-bottom-color: Khaki;
}
a:hover {
border-bottom-color: Red;
}
</style>
This way all prior links are as defined in Xara and only those on following the Placeholder box are affected.
You can change any of the named colours to http://www.w3schools.com/cssref/css_colors.asp or use a hex sextet: #123456.

The Placholder must appear lower than the text in the Page and layer gallery; I would hide it behind the black box and soft-group it.

Acorn