You can't change the "&Highlight" colour used, if that's what you mean...
"&Highlight" is an undocumented "feature" in R5, as Iris don't yet know exactly
where they're going with the functionality. Try and search for it in the Domino
Designer help file, and you'll see what I mean.
In other words, it's like unexposed Notes API calls -- use at your own peril --
and doesn't work consistently in R5.
Check out the LDD on this also, specifically this thread: