Yellow Vomit?

So

My baby is 7 days old and today for the first time he has vomited this yellow liquid 3 times. Each time has been around an hour after a 2oz bottle. He doesn’t have a temp and seems fine in himself the rest of the time. Wondering if it may be reflux, or his formula isn’t agreeing with him? Has anyone else experienced this? (We do have a doctors appointment this afternoon by the way!)