The flag of Scotland features a white saltire, a Crux decussata (X-shaped cross) representing the cross of the Christian martyr Saint Andrew (Scotland's patron saint) on a blue field. In heraldic language, it may be blazoned Azure, a saltire argent.
There is no official definition of the exact shade of blue which should be used as the field. At various times colours as light as sky blue or as dark as dark navy have been used (a selection apparently motivated by which colour of blue dye was cheapest at the time), although recent versions have largely converged on the unofficial recommendation of Pantone 300. In 2003 a committee of the Scottish Parliament declined to set an official value for the field's colour.
The Scottish saltire and field is one of the components of the Union Flag. A reversed version (blue saltire on a white field) is to be found in the Coat of Arms of Nova Scotia in Canada.