Suppose you are out there in the snow. What colour is it? What colour might it be? Snow is interesting stuff. There are many kinds of snow. They behave slightly differently, but in general the colour depends on the surroundings. Different kinds of snow will absorb or reflect amounts of energy (light). It gets more complex than that, but sticking with the generality and looking at snow in the flat it will either be in the light or in the shade.
Noon on the Farm
Looking here at the flat snow in the sun you must recall the last post. This is NOT WHITE. Relative to the darks it is very light. Since it is noon the sun is fairly high (this time of the year it is lower that in summer). The sun is hitting the snow at an angle so a lot of energy is reflected and some is absorbed. A good way to get a sun burn - I know. The sky is a blue (with yellow, green, and red in it). At this time the sun has gone to a cool yellow. So you are pretty sure these colours will be in the snow. These colours often mix to some greyed (yellowed as in complement) version of violet. There is NO FORMULA. You have to observe. At least the time of day and the conditions give you some idea of what to look for. If it was early in that day the sun would most likely be closer to orange. Late in the day closer to red. But you have to observe. When mixing that colour you have to compare your mix to the subject and make corrections. Just like a block study. So what colour would you expect to be in the shade?