Elementalist's Palette

The mana added by the last ability doesn't all have to spent on the same cost.

The mana added by the last ability can be used only to pay costs with at least one {X}, but it can be used to pay for any part of that cost, not just the {X}. That {X} could be in a spell's total cost, an ability's activation cost, or a cost you're asked to pay as a spell or ability resolves.

If you cast a spell with multiple {X} mana symbols in its cost, the first ability triggers only once.