Giorno didn't just get a sick dye job, he also got a sick hairstyle. He definitely got like +80 points in charm.Technically Dio himself wasn't 100% vampire since only his head was still vampiric, so giorno is just like 3% vampire and i guess all that does is making 4 out of 5 party members think you're a cool guy and maybe surviving some bullshit.
Oh and giving the kid a sick hair dye, thanks puberty