Does Phyrexian mana count toward devotion when paid with life instead of colored mana?

Devotion counts the number of colored mana symbols in the mana costs of permanents you control (CR 700.5). The key is that devotion looks at the printed mana cost of the card itself, not at how the mana was actually paid when the spell was cast.

A Phyrexian mana symbol such as {W/P} is a colored mana symbol — specifically, it is a hybrid Phyrexian symbol that represents either one white mana or two life (CR 107.4f). Because it contains a color (white, in this example), it counts as one colored mana symbol for devotion purposes.

Whether you paid {W} or 2 life when you cast the spell is completely irrelevant to devotion. Once the permanent is on the battlefield, the game looks only at what symbols appear in its printed mana cost (CR 700.5). The payment choice during casting has no lasting effect on the card's mana cost.

Example: You control Apostle of Purifying Light, whose mana cost is {1}{W/P}. It contributes 1 to your devotion to white — the {W/P} symbol counts — even if you paid 2 life instead of {W} when casting it.

Note: If a card has multiple Phyrexian colored symbols (e.g., {G/P}{G/P}), each symbol counts separately toward devotion for that color, again regardless of how each was paid.