驳
This bo2 depicts a horse马ma3 of mixed colors, the counting sticks on the right half (爻yao2 depicts the inlaid markings of a trigram and by extension counting rods) indicate the NUMEROUS爻 colours of this horse. The original character also means cross-breed, mixed race, since a horse with more than one colors was that. But in modernity it means variegated (which is a fancy word for multi-coloured), refute, contradict, a barge; possibly because check, verify, test is also a horsey character namely yan4验
反fan means reflect back 反对， 反映， 反问， 反驳
so reflect back a proof means to refute.
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