Dryad's Caress

• WWizards of the Coast2005-10-01
  Official Ruling
  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.
• WWizards of the Coast2005-10-01
  Official Ruling
  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.

Rulings via Scryfall