beauty is only skin deep(a person's character is more important than their outward appearance) phrase
внешность обманчиваphrase {f}
appearances are deceptive(Appearance is not enough to judge anything or anyone) phrase [UK: ə.ˈpɪə.rən.sɪz ə(r) dɪ.ˈsep.tɪv] [US: ə.ˈpɪ.rən.səz ˈɑːr də.ˈsep.tɪv]