why would a baby's arm turn red when a tourniqet is applied?

i've been a paramedic for five years and placed enormous amounts of tourniquets on all ages and nobody typically turns purple. I would think red would be more normal than purple? many people don't change color at all.

later

Had you kept the tourniquet on long enough, the baby's arm would have indeed turned purple. This is a question of oxygen extraction. Remember that venous blood is still reasonably saturated (SvO2 is usually ~75%). With prolonged venous occlusion, more and more oxygen would be taken out of the blood to support local metabolism.

Hope this helps,
doepug

I know that this may hold little physiological relevance to the topic at hand, but does the fact that patients with preipheral vascular disease commonly get dependent rubor have anything at all with the topic at hand?