I spend eons of time trying to set the colors so they are visible, but can not find a way to set the color for notes for UN-selected tracks in PRV.    I do want to see them, but it appears that sonar uses some "washout the hue" strategy based on the foreground color, and this often makes the non-foreground notes nearly invisible.  

Would a dark PRV background help?

That gets difficult, because whatever is the background for PRV, unfortunately, is the background for Event List too.   A great balancing act with what we are given.   A clumsy workaround has been to make the background in the blue hue range and all the tracks different shades of red, so that unfocused tracks at least show up as faint pink.