When _all_ the rays of which sunlight is composed are reflected in equal proportions we get the impression of white light. Dust and haze in the air reflect all rays strongly and give a whitish color to an otherwise blue sky. Brilliant white clouds appear white, because they are reflecting all rays equally. Clouds or portions of clouds appear black when they are in shade or, at times, by contrast with portions that are more strongly illuminated, or when they are moisture-laden and near the point of saturation, when they are absorbing more light than they reflect. At sunrise and sunset, when the light that falls upon the clouds is richest in red and orange and yellow, clouds reflect these colors to our eyes, and we see the brilliant sunset hues which are more intense the more the air is filled with dust and impurities.