The Dutch are a deeply patriotic bunch. Here are three things to watch out for.
The colour orange
You cannot avoid the colour orange. On Queen’s Day, during football matches, at the ice rink – it is everywhere. Oranje is the nickname given to Dutch national sports teams thanks to their – often – orange kit.
The nickname comes from the Dutch royal family, the House of Orange, founded when Willem I, the first Dutch king, inherited the title from the French noble family. The colour has now become a symbol of Dutch pride – and don’t the rest of us know it.
National anthem
The Dutch national anthem, the Wilhelmus, is said to be the oldest national anthem in the world. Written from the perspective of William of Orange (not a king but a stadhouder), it dates from the 16th century but only officially became the Dutch anthem in 1932. The opening stanza appears to refer to William as being of German blood, but this is disputed by some experts. William of Orange also rather strangely sings of his allegiance to the Spanish king.
Proclaim your Dutchness with pride
Flags
As well as public buildings, many Dutch private homes have their own flagpole and fly the flag on ceremonial days. Strict protocol applies. The rules for public buildings are divided into ‘limited flag days’, such as royal birthdays, and ‘extended flag days’, like Liberation Day (May 5), when all public buildings fly the flag. On royal birthdays the custom is to fly the red, white and blue national flag alongside an orange pennant representing the House of Orange.
Be sure to take them down before it gets dark or you will be breaking the rules.
Note: Rucksacks or other bags hung outside houses on flagpoles in May and June indicate that someone in the house has successfully passed their school leaving exams.
The Netherlands by numbers 
Sorry, but the Dutch only are a deeply patriottic bunch if it concerns football. In no other case Dutch people are patriotic or nationalistic. If they are then they are either in the army (and therefore politically right winged) or they are very right winged bartigers who want every non-western foreigner to leave the country forgood.
Actually the fast majority of Dutch people are very globalistic and are real “wereldburgers” (world citizens) except when it comes, as said, to football.
The National anthem, many Dutch do’t even know what they sing and are always complaining that “ik ben niet van Duits bloed” (I am not of German blood) However it has nothing to do with Germany. ” Duytsch or Dietsch is Germanic (NOT German) and originally means ” own people ” . It was used to denote ‘ vernacular ‘ as opposed to Latin. You will find the word “Nederduits” as description until far into the 19th century and it just means “Nederlands”. the English word Dutch is derived from this as well. The Anthem is an introduction, a promise and a prayer in one. You can find the old Dutch and New Dutch version side by side on http://nl.wikipedia.org/wiki/Wilhelmus. The melody is from http://nl.wikipedia.org/wiki/Wilhelmus but in a very different tempo and intonation, you have to listen very carefull to recognise the melody of the anthem in it. only in the last bit you can clearly recognise it
I think calling it the oldest national anthem in the world is overstating it, from 1815 untill 1932 the official anthem was “wiens neerlands bloed” because the Wilhelmus was seen a “unfit” because it was used by the orangists in the 18th century and could be seen as calvanistic by the South Dutch (now known as Belgians). it was written by Johann Wilhelm Wilms based on a poem written by Hendrik Tollens
oops, the melody is from “O la folle entreprise du Prince de Condé”, sorry for that 😉