Overall, Born is small (smaller than swap and ink) and although he seems like a 'misunderstood' child, he can still give you a bad time.
Sans has a rainbow scarf, made from the same material as papyrus's scarf. The grey bits are dust. From before Frisk's reset. Sans is wearing a Chara jacket to remind him of his failed attempts of saving his universe. Sort of like how Geno changed his name to remind him of his failure. But Born also wears a Frisk shirt inside the jacket. His eye colour differs on how he feels. Unlike the star sans' his eye shape stays the same but he simply uses ALL the sorts of magic. He has a crack in his skull from the many mental break downs in the genocide timeline. The scarf usually covers part of his face.