How would human appearance be different from what it is now if our circulatory system used Hemocyanin for oxygen transport instead of Hemoglobin?
Limitations, restrictions, additional details, etc. :
Hemoglobin can still be present for any functions, other than oxygen transport, it might perform currently, but only in the absolute minimum quantities needed for those functions, and only if Hemocyanin cannot perform those same functions instead. Hemoglobin should be removed to the maximum extent possible without compromising critical biological functions other than oxygen transport, and Hemocyanin should replace any and all Hemoglobin possible, in as many functions as it can perform in the stead of Hemoglobin.
Oxygen transport functions should be taken over utterly and completely by Hemocyanins, in whatever quantities needed to match the oxygen transport capacities of the now missing Hemoglobin. In other words, any difference in efficiency should be made up for in quantity.
This question is about appearance changes, but bonus points for any other unusual side effects this type of change might cause.
If a reason for the change is needed, let's say Aliens have been abducting humans to keep as pets, and are using combinations of selective breeding, transfusions, and direct gene manipulation to achieve their desired aesthetic in their pet population (like how humans breed dogs and cats, etc.). Or handwavium, whichever you prefer.