Not all of them are.
While there might be some teams that have partly pink team clothing, there's only ONE pink jersey that's important, and that's the one worn by the overall leader.
Giro di Italia was born pretty much the same way as Tour de France was, a newspaper decided to host a sports event to generate interest and sell more copies.
In france that newspaper was printed on yellow-dyed paper, in Italy it was pink.
And before the days of readily available, up-to-date media, the different color jerseys were a helpful tool for spectators to know when a top rider was passing by.
The leader is given a pink jersey to wear. It is pink because the newspaper that started the Giro (La Gazetta dello Sport) was printed on pink paper.
Ivelin Giro is 5' 8".
Giro dell'Appennino was created in 1934.
Münsterland Giro was created in 2006.
Mario Giro was born in 1958.
Giro City was created in 1982.
Giro - company - was created in 1985.
Giro d'Italia was created in 1909.
Giro d'Oro was created in 1983.
Giro del Trentino was created in 1962.
Giro del Friuli was created in 1974.
Giro di Lombardia was created in 1905.