On a steel car, I don't think the paint would make any difference.
But I've got a 2006 Corvette, so the body is various types of plastic. It still shows up on radar because the radar signal goes through the plastic body and reflects off the pieces of metal. Somewhat reduced compared to the typical tin car but still plenty to get clocked, just like motorcycles can get clocked. Laser is like any other red car, which I presume to be highly reflective.
My current color is bright red (Victory Red), I'm wondering if the metallic red (Crystal Red) would show up more on either radar or laser. The tiny metal particles in the paint might reflect back both radar and laser, or there is a small possibility they might scatter it in different directions and produce less reflection.