They appear red. Light waves from an object speeding toward you will have shorter wavelengths.

VOA: special.2009.04.29

Light waves from an object speeding away from you will stretch into longer wavelengths.

VOA: special.2009.04.29

Instead of collecting light, the 25 meter wide telescopes collect radio waves.

VOA: special.2009.01.20

Outside waves and winds beat the light house with giant hands.

VOA: special.2010.05.08