CO位河牌最小加注彩虹面（CO River Min-Raise Rainbow）

Term Composition

This term consists of three core elements:

• CO: Cutoff (one seat before the button), the first position to the right of the button. It is a middle-late position with positional advantage.
• River Min-Raise: The minimum raise on the river, typically equal to the current bet size (i.e., raising to double the bet). A min-raise is often used for probing, value, or bluffing, but its strength is usually weak.
• Rainbow: A rainbow board, meaning the community cards on the river are all of different suits (e.g., three or four cards are ♠♥♦♣), eliminating the possibility of a flush. Therefore, hands do not need to consider flush draws.

Strategic Significance

On a rainbow river board, since there is no flush threat, players focus more on pairs, straights, or high card combinations. A min-raise from the CO player on the river usually indicates one of the following intentions:

• Thin Value Raise: Holding a medium-strength made hand (e.g., top pair top kicker, two pair), hoping to extract additional value from weaker hands.
• Blocking Raise: Testing the opponent's reaction with a marginal hand; folding to a re-raise.
• Bluff: Using the rainbow board to reduce the opponent's calling range, but a min-raise bluff has low success rate since the cost to call is low.

Notes

• A min-raise on the river is very obvious and easily seen through by experienced opponents, so it should not be used frequently.
• The rainbow board reduces the possibility of flush bluffs, so a CO raise is more likely to be a made hand rather than a draw.
• It is necessary to combine analysis of opponent type and preflop action. For example: if the opponent raised preflop and continued betting, a CO river min-raise may indicate top pair or middle pair.