Doflamingo's sweating can be caused by both fear or anger[
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]. That rules out sweating as indicator either or because it can be both. Anger is also indicated by the face flushing, the brows moving downward and inward, clenched jaw, and perspiration when anger is intense.[
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]. Doflamingo exhibited all of those traits, including the face flushing, which is what prompted Buffalo to comment on the color of his face and indicated by two panels of his face getting red. Fear can also cause this, but mostly cause the face becoming pale, which isn't the case here especially because Doflamingo's veins in his face are bulging. Anger can also cause frantic and panicked tones, which is why Doflamingo shouted for Law to just name his demands. He also did that to formulate his counterstrategy, which ended up being the false printing.