What Causes Blueish Coloring Around Mouth, Eyes And Nose?

ok... My son (7yr old) has Pneumonia and was admitted to the hospital and treated with oxygen as he had blood oxygen level 84 after a day and a half they sent him home with blood oxygen of 95(ish) follow up with doctor 2 days later has it at 92 today around his mouth and nose by eyes look blueish took him by the Dr and they checked they said that his blood oxygen was 96 but nurse was concerned with his color and then sent us on our way... should I be concerned?