Face full of Lies
Someone who lies so much their face is like a neon sign screaming 'LIE!' in every color.
My brother said he didn't eat my snack, but his face was like he was about to confess to a crime.
My teacher said I did my homework, but her face looked like she was trying to hide a secret.
My dad said he didn't break the lamp, but his face was like he was about to get in trouble.