Blue colour tongue discoloration in new born

My baby is 1 month old. Yesterday I have noticed his tongue was in blue colour. When checked with pediatrician, he said it's normal unless Lips, hand and leg turns blue. Checked his heartbeat and pulse rate. Everything was normal. Any mommy experienced this earlier? Could you plz clarify me? I am worried #pleasehelp #1stimemom #bluecolourdiscoloration #bluecolourtongue