Flag UK St Andrew mid blue

Background

The Scottish heraldic term for an X-shaped cross is a 'saltire', from the old French word saultoir or salteur (itself derived from the Latin saltatorium), a word for both a type of stile constructed from two cross pieces and a type of cross-shaped stirrup-cord In heraldic language, it may be blazoned azure, a saltire argent The tincture of the Saltire can appear as either silver (argent) or white, however the term azure does not refer to a particular shade of blue

Throughout the history of fabric production natural dyes have been used to apply a form of colour, with dyes from plants, including indigo from Woad, having dozens of compounds whose proportions may vary according to soil type and climate; therefore giving rise to variations in shade In the case of the Saltire, variations in shades of blue have resulted in the background of the flag ranging from sky blue to navy blue When incorporated as part of the Union Flag during the 17th century, the dark blue applied to Union Flags destined for maritime use was possibly selected on the basis of the durability of darker dyes, with this dark blue shade eventually becoming standard on Union Flags both at sea and on land Some flag manufacturers selected the same navy blue colour trend of the Union Flag for the Saltire itself, leading to a variety of shades of blue being depicted on the flag of Scotland

These variations in shade eventually led to calls to standardise the colour of Scotland's national flag, and in 2003 a committee of the Scottish Parliament met to examine a petition that the Scottish Executive adopt the Pantone 300 colour as a standard (Note that this blue is of a lighter shade than the Pantone 280 of the Union Flag) Having taken advice from a number of sources, including the office of the Lord Lyon King of Arms, the committee recommended that the optimum shade of blue for the Saltire be Pantone 300 Recent versions of the Saltire have therefore largely converged on this official recommendation (Pantone 300 is #0065BD as hexadecimal web colours)

The flag proportions are not fixed, however the Lord Lyon King of Arms states that 5:4 is suitable (Flag manufacturers themselves may adopt alternative ratios, including 1:2 or 2:3) The ratio of the width of the bars of the saltire in relation to the width of the field is specified in heraldry in relation to shield width rather than flag width However, this ratio, though not rigid, is specified as one-third to one-fifth of the width of the field

http://en.wikipedia.org/wiki/Flag_of_Scotland