The Dutch and Luxembourg flags
These two flags are used as civil and state flags.
The Dutch flag
As the oldest tricolour banner of the European nations, the flag of the Netherlands, with the three red, white and blue horizontal stripes, has influenced many countries in the choice of their national emblem (including Russia under Peter the Great) and would have even served as a model for the flag of France.
Originally, the Netherlands did not have any gathering banner and stuck to the flags of the provinces composing the country. A first flag was born during the struggle against the Spanish domination in the second half of the XVIth century. The original colours were orange, white and blue, presumably because of the colours of the arms of William Ist of Orange-Nassau, leader of the independence movement. The red-white-blue flag was adopted by the United Provinces in the middle of the XVIIth century and the explanations of this change remain largely controversial.
The current flag was adopted by Decree in 1937.
The Luxembourg flag
The flag of the Grand Duchy of Luxembourg looks very much alike the flag of the Netherlands. Nevertheless, it differs in its blue colour: Luxembourg sky blue is lighter than the blue overseas of the Netherlands. Moreover, its proportions are slightly different.
Due to their similarity, it seemed natural to think that the flag of the Grand Duchy derives from that of the Netherlands. And all the more so since that both countries were ruled by the dynasty of Orange-Nassau from 1815 to 1890. However, the flag would have appeared for the first time during the events that followed the French revolution of 1830 and the manifestations of Luxembourg's people in favour of the rebellion movement of the South provinces against William Ist, King of the Netherlands and Grand Duke of Luxembourg. These events make implausible this relationship.
As often, the colours of the flag would find their origin in the ancient coat of arms of the nobility of the region.
It might also be that the choice of colours was influenced by the French tricolour flag. Then, the drawing would have only been forced by the necessity to differentiate the flag of the country from the revolutionary emblem. If it were the case, why the distinction did not directly happened at the level of the choice of the shades of colour ?
Have all these reasons delayed the formal adoption of the flag of the Grand Duchy, which dates back to 1972 only ?