Colour Idioms - White

black and white 

if we have situation in which it’s easy for someone to understand what’s

wrong and what’s right, we say ‘it’s black and white 

As white as a sheet  

if someone is very pale because they are ill or shocked or scared, we say they’re as

white as a sheet 

A white-knuckle ride 

if something is very exciting or scary, we call it a white-knuckle ride