Some people turn white with rage. He could of course be embarrassed at the sight of the man he has allegedly mistreated, but because of the inconsistencies I have detected in Wickham's story I have doubts of its truth at this stage.

Wickham's actions so far in the novel seem to suggest he has no sense of shame (a man who did could hardly say "Till I can forget his father, I can never defy or expose him." when in the very act of exposing the subject of the conversation to a young woman he met the previous day) but again embarrassment is not the only reason to go red - some people do go red with anger or frustration. And on the other hand one can go white with fear. I think any final decision must wait until and if we see one of these men when he is definitely angry or definitely embarrassed or definitely afraid.