Nipple discolouration 1 month post op BR? (Photo)

Thank you for your question and picture.  It is difficult to tell from just one view, but as long as it doesn't get darker and as long as you don't start to lose sensation, then keep observing.  If however, it starts to worsen, then see you PS ASAP.

It would be very unusual for your nipple to lose circulation 5 wks after a breast reduction. Especially since your two breasts have no bruising and look the same. I don't think the color change is anything to be worried about.