Pure white. What better to symbolise whiteness than snow? Not only the intensity of colour on a bright winter’s day, but also the purity of untrodden snow is summoned up by the simile. Shakespeare used this association to good effect in as pure as the driven snow.

We have to bring out the big guns for the origin of this one. Chaucer, Shakespeare and the Bible all contain versions of white as snow. From Shakespeare’s Hamlet, 1602:

… What if this cursed hand
Were thicker than itself with brother’s blood,
Is there not rain enough in the sweet heavens
To wash it white as snow? …