The national flag of Romania is a tricolour with an aspect ratio of 2:3 (width-to-length) and has equal vertical stripes of blue, yellow and red.
The colors represent the principalities of the two largest regions (Wallachia and Moldavia) in Romania which united along with Transylvania to form the Kingdom of Romania in 1881. Red and yellow represent the principalities of Wallachia; and red and blue represent the principalities of Moldavia. In 1821, for the first time a meaning was attributed to them: Liberty (sky blue), Justice (field yellow) and Fraternity (red)
The tricolour was first adopted in Wallachia in 1834 but the order of the colors were changed. In June 1848, the revolutionaries that year adopted a flag with horizontal stripes of blue, yellow and red for Wallachia. The following month, July 1848, a decree was passed changing the horizontal stripes to vertical stripes with the same order of colors. Then in 1866, under Article 124 of the 1866 Constitution of Romania provided the current design of the national flag with the order and placement of the colors later decided by the Assembly of Deputies in 1867.
Some odd facts about this tricoloured flag. The Romanian flag is very similar to the flags of two countries - Andorra (which is a sovereign landlocked microstate in Southwestern Europe, located in the eastern Pyrenees mountains and bordered by Spain and France) and Chad (which is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the southwest and Niger to the west. It is the fifth largest country in Africa in terms of area). The flag of Andorra has the same shades of color except it has a coat of arms in the middle. The flag of Chad is very similar on a different shade of blue which is a bit darker. This caused an international discussion in 2004 but neither countries changed their flags.
The official pantone colors of the flag of Romania are blue (280c), yellow (116c) and red (186c).