text: why is the sky blue?   particularly in desert areas, where the sky may appear white, brown, or some other color. dust is also responsible for the pinkish sky on mars, as seen in the photographs returned from the viking landers.  if the atmosphere contains lots of dust, the direct light from the sun or moon may occasionally get some quite unusual color. sometimes, green and blue moons have been reported. these phenomena are quite rare though---they happen only "once in a blue moon...." :) the dust responsible for these unusual color phenomena is most often volcanic in origin. when el chicon erupted in 1982, this caused unusually strongly colored sunsets in equatorial areas for more than one year. the much bigger volcanic explosion at krakatoa, some 110 years ago, caused green and blue moons worldwide for a few years.  one possible exception to the above discussion is if the clouds on the planet are composed of a strongly colored chemical. this might occur on jupiter, where the clouds are thought to contain sulfur, phosphorus, and/or various organic chemicals.  it's also worth pointing out that the light of the planet's primary is quite insignificant. our eyes are highly adaptable to the dominating illumination and perceive it as "white," within a quite wide range of possible colors. during daytime, we perceive the light from the sun (6000 k) as white, and at night we perceive the light from our incandescent lamps (2800 k, like a late, cool m star) as white. only if we put these two lights side-by-side, at comparable intensities, will we perceive a clear color difference.  if the sun was a hot star (say of spectral type b), it's likely we still would perceive its light as "white" and the sky's color as blue