My son and I built a school bus that used two flashing red leds. It was real hit with the other boys, won a special prise for "Most Inovative", but not a winner on the track! Anyway, if I were to do it again, it'd be easier to simply drill tiny holes and run fiber optic cable and flatten the ends with a solder pencil to broaden the look/light. Then you could simply use 1 white led and run the necessary colored fiber wire. You can buy various colored fiber wires for cheap at archery pro shops. Finally, keep the battery low and towards the back of the car. Weight should be placed close to the rear axle for best performance.... and use powdered graphite lube on the wheels if your pack allows. I polished the nails to a mirror shine and that allows the wheels to spin for several seconds longer than normal.