It does work but only to a certain point. Thats why I said "from a distance". With a mat color you decrease significantly the reflectiveness of the car so from far away, the laser gun will not be able to get a strong enough reflection in order to get a speed reading.

As you get closer there will be a point were he will get a reading, although in this case most likely because he will be finally able to get a licence plate or headlight shot in, and then the car's paint will have no effect.

Laser guns now a days can reach up to 1000m away and cars from that distance look very small through the telescopic view. Even a normal black color car has an advantage from very far away over a silver one for example, but not much. Cars with no front licence plates as well, and cars with folding headlights too.

But if you want any serious protection you can only rely on a laser jammer