The star is Capella (the golden star), the 6th brightest star in the sky besides the sun. It blinks fiercely red, green, blue - all colors of the rainbow, when it's low on the NE horizon because of the light refracted in the atmosphere. As it rises higher in the sky, the colored blinking stops because you're seeing it through less atmospheric conditions. So it doesn't actually disappear. It's there the whole time - just looks differently from higher above.