They can be synonyms i.e. Νέος χρόνος or Καινούργιος χρόνος = New Year Νέος can mean young, but καινούργιος doesn't. Νέος άνθρωπος = young person (not καινούργιος άνθρωπος, unless God decided to give it a second shot!)

Νέος, usually refers to age. Νέος άνθρωπος = young person Καινούριγιος = New (it does not refer to age) but Νέος also can also mean new.......and they are synonyms Νέος χρόνος = New year or Καινούργιος χρόνος Νέος στη δουλειά = new at work Or Καινόυργιος στη δουλειά

Generally they are synonyms (with slight diferences). Νέος can also mean young (man)

Σας ευχαριστώ πολύ! Τώρα είναι καθαρά.