Cavern of souls

[Juggalonoke]

Can {cavern of souls} second tap ability be used to select a colorless mana?

[Dudecore2012]

Nope. Says "of any color"

[BlackJester]

Can {cavern of souls} second tap ability be used to select a colorless mana?

Why would want a colorless mana?

[Juggalonoke]

Commander.... I use karn as a general and eldrazi annihilators in deck and them not being counted as I play them would be nice

[BlackJester]

Based on rule 903.9 "if non-commander colored mana would be added to your mana pool, colorless is added instead.". I'm paraphrasing, but you could chose any color and still wind up with colorless.