Historical Rules · 14 June 2019
Rule 107.4
Official source text from the 14 June 2019 Rules release
The mana symbols are {W}, {U}, {B}, {R}, {G}, and {C}; the numerical symbols {0}, {1}, {2}, {3}, {4}, and so on; the variable symbol {X}; the hybrid symbols {W/U}, {W/B}, {U/B}, {U/R}, {B/R}, {B/G}, {R/G}, {R/W}, {G/W}, and {G/U}; the monocolored hybrid symbols {2/W}, {2/U}, {2/B}, {2/R}, and {2/G}; the Phyrexian mana symbols {W/P}, {U/P}, {B/P}, {R/P}, and {G/P}; and the snow symbol {S}.