Dryad's Caress

Instant

You gain 1 life for each creature on the battlefield. If was spent to cast this spell, untap all creatures you control.

2005-10-01:
The spell checks on resolution to see if any mana of the stated color was spent to pay its cost. It doesn’t matter how much mana of that color was spent.
2005-10-01:
If the spell is copied (such as with Twincast), the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.