Some people love it, some people hate it, but we can all agree snow is white. Or so we thought. Colored snow is a naturally occurring phenomenon is several parts of the world, and not just the black and gray slush that you find along the roadways as winter drags on. Snow can be found in red, green, blue, orange and even the questionable color yellow.
One of the most commonly occurring sources of unusually colored snow is found in Alpine regions above 10,000 feet. A form of algae known as Chlamydomonas Nivalis is actually dependent on snow to thrive. This algae forms under snowfall and filters ultra-violet light from the sun to melt the snow just enough to obtain the liquid water it needs to grow.This process has the secondary effect of turning the snow a red or green color and even giving it a scent similar to watermelon.
In 2007 residents of Omsk, Russian in Eastern Siberia were treated to a smelly and unusually colored snowstorm. For several days a oily, orange colored snow blanketed the city. Despite the brilliant color of the snow it was later discovered the cause of the hue was fairly concerning and caused by chemicals from nearby oil refineries mixing with the snow in the atmosphere.
In reality snow only appears white it is actually an extremely pale blue. If you were to look at individual snowflakes this hue would be more apparent. Light conditions as well as the concentration of the precipitation make it appear white.
Frank Zappa once famously warned us of yellow snow and this warning should be heeded. According to scientific research the only occurrences of yellow snow are caused by urine mixing with the snow.