A lot of you are mentioning painting your cap guns, or whatever fake gun a bright colour. While that helps, it doesn't exactly solve the problem. A lot of police involved shootings occur in dark areas, at night (parties, trick-or-treating, etc), where there isn't a lot of light. All the Officer can see is the (dark) outline of a weapon.
Just do what Treadstone said, leave the gun and holster behind. Nobody will even care. It's a lot better than the alternative.