George,
We currently use the ADS-B standard of Cyan (Aqua), Yellow, and Red for alert status. Have you tried to add the High Contrast Traffic Instrument? I like it as I set the visibility to unlimited distance and +/-3500 vertically. Then on the Traffic Instrument I set it to 5nm of distance, so when traffic shows on the Radar inst, I know I should be able to get a visual on it. Otherwise, typically traffic that is over 5nm away and over +/-3500 feet is not much of a concern.
There may be an opportunity to outline, solid shade or even shadow the icon more to up the contrast. We want to keep the colors as part of the ADSB standard the FAA has set, so there is less industry confusion. We'll keep an ear out for any issues here. Thanks for your feedback and honesty.