I believe that since the red color represents the peak and the blue corresponds to the minimum values (which are negative). Green represents values close to 0. But if you look at the abs values in the first figure, they are all positive. So again red represents the maximum whereas blue represents the minimum values which are close to 0. In the last figure, when you chose the scalar operation to abs, it means you no longer will see any negative values so now blue corresponds to 0.
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