On this day April 12, 1606
The Union Flag is adopted as the flag of Great Britain to represent this regal union between England and Scotland was specified in a royal decree, according to which the flag of England also representing Wales by implication.
This royal flag was at first only for use at sea on civil and military ships of both Scotland and England.
In 1634, King Charles I restricted its use to the monarch’s ships. Land forces continued to use their respective national banners.
After the Acts of Union 1707, the flag gained a regularised status, as “the ensign armorial of the Kingdom of Great Britain”, the newly created state.
Various shades of blue have been used in the Saltire over the years. The ground of the current Union Flag is a deep “navy” blue, (Pantone 280), which can be traced to the colour used for the Blue Ensign of the Royal Navy’s historic “Blue Squadron”. (Dark shades of colour were used on maritime flags on the basis of durability).
The currently accepted flag of Scotland however uses a lighter “royal” blue, (Pantone 300), following the Scottish Parliament recommendation of 2003.