Long dark object with a white light in the front and a very bright blue light at the rear glided silently above our vehicle at 150 ftDriving north on HWY 97 approaching Janus Bridge south of Tonasket just after dusk when a long dark object approaced from behind on our right and glided unexpectedly directly over our vehicle where we were startled to see it at a low altitude, perhaps 150 to 200 ft above us. We could see a long dark structure with a white light at the front end and a very bright blue light at the rear. The object proceeded very quickly and absolutely silently up the river valley toward the town of Tonasket. We were able to see it in the distance for a minute or two before it disappeared in the distance. Just before it disappeared the rear blue light began changing color to red and white and began flashing. The structure had no wings and in trying to describe it to each other we all three agreed that it resembled a dragon fly with no wings. My husband had the impression that it was about 200 feet long. I would say that it appeared to be 60 to 100 feet long. The difference, I believe, is in the estimate of how high above our vehicle it was.