Convoke (CR 702.51) allows you to tap untapped creatures you control as you cast a spell with convoke. Each creature you tap pays for either one generic mana (the colorless number in the cost) or one mana of a color that creature has. This means a colored mana symbol in the cost can absolutely be paid by tapping a creature of that matching color.
Specifically, CR 702.51b states: 'Each creature you tap while casting a spell with convoke pays for {1} or one mana of that creature's color.' So a red creature can pay for {R}, a green creature for {G}, and so on. A multicolored creature can pay for one mana of either of its colors.
Important limits to keep in mind: each creature can only pay for one mana total (not multiple symbols), and you can only tap creatures you control that are already untapped at the time you cast the spell. Convoke does not change when you can cast the spell — it only provides an alternative way to pay part of its cost (CR 702.51a).
Concrete example: You cast Chord of Calling with mana cost {X}{G}{G}{G}. You tap three green creatures to pay for all three {G} symbols, then tap additional creatures (any color) to help pay for {X}. You pay the remainder of {X} with normal mana. The green creatures each satisfied one {G} in the cost.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.