All babies undergo some hypoxia during labor and most babies are born a little purpleish gray. As a matter of fact, when I give APGARS, I've never given a 10-10 because I've never seen a baby who was 100% pink at one minute. It usually takes about 5 mintues, minimum, to get them pink to the feet and hands.
Some babies are born more purple than others. I was taught to assess baby's condition during crowning by the color of the scalp: pinkish gray is a-okay, whitish-gray is still okay, purpleish-gray means there's some oxygen deprivation, dusky purple means there's more oxygen deprivation and blackish-purple means baby will probably need some form of resus. Some babies have more difficulties with crowning than others: babies who are malpositioned, babies who descend very quickly, and to a much lesser extent, babies with nuchal cords (around the neck). Babies in those circumstances tend to be a little more purple than others.
The cord clamping and cutting is a big issue. Just because baby is breathing doesn't mean that they are getting 100% of the oxygen they need through their (newly functioning) lungs. Having the placenta still pumping oxygenated blood to the baby helps a lot with oxygen perfusion and babies who have oxygen coming to them from the placenta for longer tend to pink up more quickly than those whose cord is cut immediately.
Charlotte, midwife to some awesome women, wife to Jason, and no longer a mama to all boys S ('01), A ('03) S ('08) and L ('10).