blue paper
noun
1Blue-coloured paper, typically used for packaging commercial goods, especially sugar; a sheet of this; now chiefly historical.
2A light-sensitive paper used for copying maps and plans, typically made by treating the paper with potassium ferricyanide and ferric ammonium citrate; compare cyanotype (now rare ).
Origin
Late 16th century; earliest use found in Richard Carew (1555–1620), antiquary and poet.