Does phyrexian mana count toward a spell's color identity in Commander?

In Commander, a card's color identity is determined by every mana symbol that appears anywhere on the card — in its mana cost, rules text, or anywhere else (CR 903.4). This includes Phyrexian mana symbols such as {W/P}, {U/P}, {B/P}, {R/P}, and {G/P}.

CR 903.4 explicitly states that color identity is derived from all mana symbols on the card, and Phyrexian mana symbols are mana symbols (CR 107.4f). The fact that you can pay 2 life instead of the colored mana does not remove the color from the symbol itself — the symbol still identifies a color.

This means, for example, that Gitaxian Probe has a blue color identity ({U/P} in its mana cost), even though you will almost always pay 2 life to cast it. You cannot include Gitaxian Probe in a deck whose commander has no blue in its color identity, even if you never intend to spend blue mana on it.

Similarly, cards like Slash Panther (which has {R/P}{R/P}{R/P}{R/P} in its cost) have a red color identity and cannot be played outside red-inclusive Commander decks.

The rule applies regardless of how you intend to pay — the symbol on the card is what matters, not the payment method chosen during casting.