Low oxygen content of the blood can cause blue lips. This can be due to low blood counts or due to problems with oxygenation of the blood. If it is low then your doctor would have to look for sources of low blood oxygen such as blood clots, sickle cell disease or other hemoglobin abnormalities.
The underlying cause is numerous and some are serious and with palpitations it can be heart related, but all conditions relate to a deficit of oxygen supply and it can be Obstructive Pulmonary Disease, Congenital heart defects, Emphysema, etc.
Are you taking any medication? Do you have a chronic illness? What does your physician say?