Historical Rules · 12 July 2019
Rule 107.4h
Official source text from the 12 July 2019 Rules release
The snow mana symbol {S} represents one mana in a cost. This mana can be paid with one mana of any type produced by a snow permanent (see rule 205.4g). Effects that reduce the amount of generic mana you pay don’t affect {S} costs. Snow is neither a color nor a type of mana.