The flag of historic Greece was officially adopted in 1822. It features a white cross, and a combination of nine blue and white horizontal stripes. Note that the shade of blue has varied over the years, and darker blue (shown) is now commonly used.
The cross is symbolic of the Greek religious faith and the nine stripes represent the nine syllables in the cry "Freedom or Death," one commonly used during the Greek war of independence. The white is said to reflect the purity of that struggle.