a form of proof made from a film assembly used to check the position of text and illustrations as a final stage of approval before printing. Called in the US 'blues' after the colour of the image on the proof. X Y Z

In lithography, a photographic proof made from planned-up films used to proof check the position an image on the page and page imposition on the sheet. Also known as a Blue-line or Dyeline proof.

A trade name to describe a method of copying page proofs from paper or film.

Tradename of a system of drawing reproduction based on the ammonia vapor process; the prints consist of purple lines on a white background; other colors of line and background are also available.