Darker Blue used in the Union Flag
Lighter Blue standardised in 2003
Fabric printing technology has expanded at an alarming rate over the last decade. This has led to a flood of textile products being sold online. Most of these items, which include flags, are produced with disregard to any specific regulations. The St Andrew’s Cross or Saltire has had so many variations of blue that the Scottish Parliament voted, in 2003, to standardised the shade of blue to Pantone 300 c. However, it is difficult to implement this rule due to an abundance of overseas manufacturers. At the best of times, blue colouring is notorious for inconsistencies due to unstable pigments, application surfaces, and other various reasons. Regardless, most reputable flag manufacturers endeavor to get the best possible match within reason.
When produced per se (by itself), the shade of blue for the St Andrew’s Cross flag should be Pantone 300c (or as near as damn it). This is probably better implemented by a printing process when the values can be adjusted. When it comes to a fully sewn flag, there are limited shades of blue on the MoD specification chart. Again, a good flag producer will use the closest blue available on the colour chart.
It is worth noting that, when the Saltire is incorporated within the Union flag, the shade of blue is darker. This has become accepted over the years due to historical factors when the durability of dyes was important.