Commander question

[Taysby]

Say my commander is {krenko, mob boss}.  Can I have {izzet key rune} in my deck.  I don't think so because you have to pay blue for its ability, but my friends think you can because it doesn't require colored mana to play.  Who's right?

[Pirate John]

You're right. It can't have an activated ability that requires anything besides red mana.

[Millionlittlee]

You are even though it's an colorless it, can tap for blue which makes its blue/ red

[xStrayKnightx]

In response to this question as a follow up, my mate has {Pontiff of Blight} in his Grixis Zombie deck. Is that a deck-legal card, seeing as Extort uses either Black or White? His Commander is {Crosis, the Purger}.

[Wackaman9001]

Pontiff has a colored symbol in his REMINDER text, not rules text. It is legal, since his color identity is completely black

[xStrayKnightx]

Cool. I'll let him know.