If stars come in colors, why do most appear white to the eye?
When you look up at the sky on any clear night, just about all the stars look white. Only a very few of the brightest ones appear red, yellow or orange. The problem is that the eye has two kinds of light receptor cells: rods and cones. Color vision comes from the response of the cones; however, the cones are not very light sensitive. Below a fixed light intensity, they stop responding at all. The rods, however, are very sensitive photoreceptors even at low light levels, however, they only sense black and white or more correctly they are monochromatic. When you look at the brightest stars with the naked eye, or when you use a telescope to concentrate the light that falls on your retina, the light can be above the threshold at which the cones can register color, but for the thousands of other stars in the skies fainter than these brightest stars, only the monochromatic rods see anything and do not pass on color information to the visual cortex of the brain.
