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The Greek flag contains the colors blue and white.
A Greek cross is usually located above an X. The Greek cross has a horizontal line and a vertical line. Each line will have an equal length to it.
a tau cross.
It is. Since the Greek Orthodox Church is under Christianity, the cross is a "holy symbol".
Although technically a Greek cross is "crux immissa quadrata" the answer you want is more likely to be "stauros."