page.visual_effect :highlight

This is similar to a problem I had a few weeks ago. It has to do with
the way scriptaculous does a highlight:

1) store initial state
2) do highlight
3) restore initial state by setting the element's style attribute

I bet it's storing is a semi-highlighted state, which would be pale
yellow.

And (as I found out) step #3 plays hell on your CSS classes.

That said, I don't know how to solve your problem, because I've never
done multiple highlights. You might look into scriptaculous' Effects
Queues.

Cheers
Starr