Oracle Text

Firespout deals 3 damage to each creature without flying if R was spent to cast Firespout and 3 damage to each creature with flying if G was spent to cast it. (Do both if RG was spent.)

Card Rulings

6/8/2016 This spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid mana symbol in its cost.
6/8/2016 This spell checks on resolution to see if any mana of the appropriate colors were spent to pay its cost. It doesn’t matter how much mana of that color was spent; the effect isn’t multiplied.
6/8/2016 If this spell is copied, the copy will not have had any colors of mana paid for it, no matter what colors were spent on the original spell.