The flag of Portugal is a rectangular bicolor. The field in unevenly (2:3) divided into green (on the hoist) and red (on the fly). Over the color boundary there is a lesser version of the Portuguese coat of arms , located at equal distance from the upper and lower edges. This version comprises the armillary sphere and Portuguese shield.
The design was officially adopted on June 30, 1911, less than a year after the downfall of the constitutional monarchy. After a failed republican insurrection in 1891, the colors red and green were the colors of the Portuguese Republican Party. Later, they were popularly propagandized as representing the hope of the Portuguese nation (green) and the blood of those defending it (red).
Since the foundation of Portugal, the flag was always linked to the royal arms. Actually, until 1640 there wasn’t a distinction between the national flag and the royal arms.
The first heraldic symbol associated with Portugal was the shield — with a blue cross over a white field — used by Henry of Burgundy since 1095. His son (Alfonso) used the same shield but in 1143 he changed the shield to reflect his new status (king). Sancho I, Alfonso’s son, also changed the shield following the inheritance of a not so well maintained shield. Thus the compound cross of five blue bezant-charged escutcheons–the quinas —was born. The shield suffered minor changes and it was used in about the same form until 1383.
In 1385, John I changed the personal banner and it lasted unchanged for 100 years. In 1485 new changes were made, as well as a radical change in 1495. The banner became a white rectangular with the coat of arms in the center.
In 1578 it was again modified. The royal crown became a closed three-arched crown and the number of castles was fixed to seven. By 1667 the flag was changed again to reflect the contemporary trends. But in 1707 John V changed the flag again. A red beret was added under the crown and the shield was converted into a samnitic shield. Later, John VI changed the flag again to reflect the new political situation.
In 1822 a new flag was created. This time there were to colors: blue at the hoist and white on the fly. The coat of arms was added on the color boundary and the shield was the asamnitic shield used by John V. This flag was used for 80 years, until the end of monarchy in 1910.