My ds had blue lips today but when checked out his sats and heart rate was ok. He's asthmatic and is currently on inhalers for a post viral wheeze but didn't seem that wheezy (and like I said sats were fine). He does sometimes go blue lipped when cold but he wasn't cold today. Anyone know what it could have been? Randomly with his asthma they often can't 'find the wheeze' but it's clearly there as he's short of breath and inhalers improve - not sure if this is relevant or not.
How old is he? My dd2 had this occasionally as a baby. Worried me a lot as she has a congenital heart defect. However it never seemed significant of anything and it went away. How old is your son? I think you should seek GP advice and obviously call 999 if it happens again and seems to be affecting his breathing. I wonder if it could be migraine? That can do some weird stuff.
3... he never got it as a baby - maybe started a year ago? It used to just be when cold. He didn't say he was feeling unwell when it happened but I agree migranes can manifest themselves in weird ways.