Rule 107.4e

A hybrid mana symbol is also a colored mana symbol, even if one of its components is colorless. Each one represents a cost that can be paid in one of two ways, as represented by the two halves of the symbol. A hybrid symbol such as {W/U} can be paid with either white or blue mana, and a monocolored hybrid symbol such as {2/B} can be paid with either one black mana or two mana of any type. A hybrid mana symbol is all of its component colors. Example: {G/W}{G/W} can be paid by spending {G}{G}, {G}{W}, or {W}{W}.