My cats used to love chasing a red when they were younger. Now the remaining one doesn't care so much. He also doesn't care for greens at all. After awhile they sort of caught on. I had to be very inventive to give the motion of the laser spot "prey-like behavior". I would run the spot under the couch and turn it off so it looked like it ran underneath. Have it peek around corners etc.
My dog still goes nuts for the red. He only likes the green outside during daylight. The best thing though is if you keep it still in one spot on the floor, he'll scratch at it. Sit down, stare at it for about 30 seconds, then he'll rear up and pounce on it with his front paws to try and "scare" it back into moving so he can chase it some more.
Even funnier is he knows I'm doing it with a pointer. You can take a butter knife or a magic marker wave it around like it's a pointer and he'll go nuts looking for the spot.