Flag of Greece ensign Greek Orthodox merchants (better: merchants from the Greek-dominated Orthodox "millet") were allowed to fly on their ships, combining stripes with red (for the Ottoman Empire) and blue (for Orthodoxy) colours. After the Treaty of Küçük Kaynarca, Greek-owned merchant ships could also fly the Russian flag. During the uprising of 1769 the historic blue cross on white field was used again by key military leaders who used it all the way to the revolution of 1821. It became the most popular Revolution flag, and it was argued that it should become the national flag. The "reverse" arrangement, white cross on
Flag of Greece other designs surviving until that time. No other designs and badges can be shown on the flag. To date, no specification of the exact shade of the blue colour of the flag has been issued. Consequently, in practice hues may vary from very light to very dark. The Greek Flag Day is on 27 October. The old land flag is still flown at the Old Parliament building in Athens, site of the National Historical Museum, and can still be seen displayed unofficially by private citizens. The use of the Greek flag is regulated by Law 851. More specifically, the law