Q: Why are the stars near the edges of this dark cloud reddish? The cloud contains both gas and dust particles. When light passes through the cloud, some of it scatters off the dust. Light with short wavelengths -- blue light -- is more likely to interact with a dust particle and be bounced off in some other direction. The longer wavelength -- red light -- rays are more likely to pass through the cloud and reach us. It's exactly the same explanation for the reddish colors of sunsets.