Short answers, pulled from the story.
The flag of Hungary has been officially a plain red-white-green tricolour since the 23rd of May 1957, following the removal of the coat of arms after the defeated 1956 revolution.
The Hungarian constitution, which took effect on the 1st of January 2012, officially defines the colours as representing strength (red), fidelity (white), and hope (green). An older folklore interpretation held that red symbolised blood spilled for the fatherland, white stood for freedom, and green for the pastures of Hungary.
During the 1956 anti-Soviet uprising, revolutionaries cut out the Communist Hammer and Wheat emblem from the centre of the flag and used the resulting tricolour with a hole as their symbol of resistance.
The red, white, and green colours derive from the historical Hungarian coat of arms, whose essential form dates to the mid-15th century, with the underlying arms of the Arpad dynasty appearing in the late 12th and early 13th century. The combination was already in use at the coronation of Leopold II in 1790.
Both flags use red, white, and green, but the Hungarian flag runs the stripes horizontally while the Italian flag runs them vertically. The Hungarian horizontal tricolour predated the adoption of the Italian tricolour by an Italian state by at least seven years.
Act XXI of 1848 was the first legislation to formally mandate the use of the red-white-green tricolour as a national symbol of Hungary, arising from the national freedom movement and the Hungarian Revolution of 1848.