The colours are based on lidar intensity, i.e. how much light is bounced back from a surface. This depends on the reflectivity. That's why it can see lane markings and even murals on the wall: https://www.youtube.com/watch?v=a0-JaMGivX4
Ah, thanks. So the colors are an aesthetic choice? There's no more information than one might get from greyscale? (Which is a fine thing; I love the colors.)