In the evening clour of the cloud is seem to be red sometime. why?

Dust in the air makes the clouds look red - there are winds blowing at high altitudes that can carry dust for hundred, and even thousands, of miles. The sun shining though the dust laden air makes the clouds appear red, and can make for beautiful sunsets... Light white is made up of 7 visible colours which can be seen during a rainbow.As the sun sets,white light from the sun passes through the water vapour in the air and other particles,causing the white light to break up into different colours.Since red has the longest wavelength,it is the colour mostly seen during sunset.