Does Phyrexian mana count toward a spell's colored mana cost for devotion?

Devotion counts the number of colored mana symbols in the mana costs of permanents you control (CR 700.5). A Phyrexian mana symbol (e.g., {W/P}) is a colored mana symbol — specifically a Phyrexian white symbol — and therefore it does contribute to devotion on a permanent you control, regardless of how you paid for it (CR 107.4f).

The key point: devotion looks at the printed mana cost symbols on the card, not at how the spell was actually paid for. Whether you paid the {W/P} with {W} or with 2 life, the symbol still appears in the card's mana cost and still counts as one white mana symbol for devotion purposes.

So a card with {G/P}{G/P} in its mana cost contributes 2 to your green devotion even if you paid 4 life instead of any green mana. The symbol is there on the card; that's all devotion cares about.

Example: You control a Birthing Pod ({3}{G/P}) and a Nykthos, Shrine to Nyx. Birthing Pod has one green Phyrexian mana symbol in its cost, so it contributes 1 to your green devotion, regardless of whether you paid {G} or 2 life when you cast it.

Citations: CR 107.4f defines Phyrexian mana symbols as colored mana symbols; CR 700.5 defines devotion as counting colored mana symbols in mana costs of permanents you control.