Sunset is always red in colour due to the fact that more red light is normally scattered because of aerosols in the lower atmosphere. Generally, sunlight usually have red and orange colour in them. *At sunset, the sun’s light passes farther through the atmosphere, deflecting and decreasing the blue in the air. Scattering by dust particles and pollution in the air causes the sunset to appear red. * The sunset is red because of dust particles and other pollutants in the atmosphere. The reason this happens at sunset is because of the angle of the sunlight striking the Earths atmosphere. As light hits the earth at an angle as you have during sunset it is scatters and reflects more of the red light spectrum back to the surface.
*A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight. The white light from the sun is a mixture of all colours of the rainbow. This was demonstrated by Isaac Newton, who used a prism to separate the different colours and so form a spectrum. The colours of light are distinguished by their different wavelengths. The visible part of the spectrum ranges from red light with a wavelength of about 720 nm, to violet with a wavelength of about 380 nm, with orange, yellow, green, blue and indigo between. The three different types of colour receptors in the retina of the human eye respond most strongly to red, green and blue wavelengths, giving us our colour vision.