FLAG of UKRAINE
The National Flag of Ukraine is a modern flag of Ukraine, a banner made up of two equal horizontal stripes of blue and yellow.
The blue and yellow (gold) colours were used on the coat of arms of the Kingdom of Rus' in the 14th century. They were also used on the coats of arms of Rus'es lands, princes, nobility, and cities in the Middle Ages and early modern times.
Starting in the 16th century, the Cossacks of the Zaporуzhian Army used blue and yellow banner flags in small numbers, and in the 1710s, blue and yellow Cossack flags began to prevail among the Cossack banners, often made of blue cloth with a knight in gold or red robes and gold ornaments and fittings sewn on it.
The blue and yellow flag with a red cross in the middle appeared in 1803 as the flag of the Black Sea Cossack army.
The modern blue-and-yellow flag was first publicly recorded on 25 June 1848 in Lviv, when Ukrainians of the Kingdom of Galicia and Volodymyriya hung it over the Lviv City Hall as a national flag. It was after this event that the blue and yellow flag became increasingly popular among Ukrainians, and after the 1905 revolution, it was used by Ukrainians of the Dnieper Ukraine.
In 1917-1921, during the Ukrainian Revolution, this flag was the national flag of the Ukrainian People's Republic and the Ukrainian State.
Later, during the Soviet era, the blue and yellow flag was used clandestinely, and its use in the USSR was punishable by two years in prison.
In 1991, after the collapse of the USSR, this flag was de facto used as the national flag of independent Ukraine. On 18 September 1991, the Presidium of the Verkhovna Rada of Ukraine legally established the status of the country's official flag.
On 23 August, Ukraine annually celebrates National Flag Day.
https://en.wikipedia.org/wiki/Flag_of_Ukraine#History