Currently there is only a set amount of hard coded options dealing with the colour of combat and other feedback text. During a fight (with or without a group) the volume of text flowing past can make it easy to miss important lines of text, ie the ones that usually mean life or death.

For example, when fighting the marrow guards at Valkor's castle, you want to know when a marrow uses it's Ethereal Blade ability so that it can be dispelled quickly.

What I suggest is that players have the option to set a number of their own text strings with colour options, including a background colour (if possible).

So when "Ethereal Blade" (or whatever other strings of text you have defined) pops up in a line of combat feedback, that whole text line is displayed as your chosen colours rather than the hard coded default colour setting.

Used to have this feature in an old MUD I once played, it was called Highlight Strings and it was pretty nifty.