The flag of Spain, as it is defined in the Spanish Constitution of 1978, consists of three horizontal stripes: red, yellow and red, the yellow stripe being twice the size of each red stripe. Traditionally, the middle stripe was defined by the more archaic term of gualda, and hence the popular name rojigualda (red-weld).
The origin of the current flag of Spain is the Naval Ensign of 1785, Pabellon de la Marina de Guerra under Charles III of Spain. Throughout the 18th, 19th, and 20th centuries, the color scheme of the flag remained intact, with the exception of the Second Republic period (1931-1939), being the only changes centered on the coat of arms.
The Spanish coat of arms:
The current coat of arms was adopted on December 19, 1981, when it replaced the model of 1977 which, in turn, replaced the model of 1945, considered the official coat of arms of Francoist Spain.
The present coat of arms consists of a quartered shield, each of the four quadrants representing one of the four kingdoms that were merged to form a unified Spain at the end of the 15th century. Namely, the kingdoms are: Castile, represented by the gold castle on red; Leon, represented by the purple lion on silver; Aragon, represented by the four red bars on gold; and Kingdom of Navarre, represented by the linked gold chains on red. Also the christian kingdom of Granada is represented by the pomegranate fruit in the bottom of the coat of arms. In the centre of the shield is an inescutcheon with the emblem of the reigning Spanish royal Family, House of Bourbon (a blue oval with a red-edged border containing three golden fleur de lys). The coat is crowned with the Spanish Royal Crown and guarded on each side by two columns crowned and charged with a red ribbon with the motto "plus ultra" in gold letters. The motto means "further beyond" in Latin).
The columns on the Spanish coat of arms are the mythological Pillars of Hercules (of the Strait of Gibraltar, gateway to the Atlantic Ocean), and considered the end of the known World in ancient times. The "Plus Ultra" motto replaced the former "Non Plus Ultra" (something like "No further from here") before the discovery of America, since Spain was considered "the Westernmost point" on Earth (thus, "no further from here").