(His name is Vojtech in Czech and Wojciech in Polish). He became bishop of Prague in 983. He met with intense opposition from the nobility. He withdrew to Rome but was sent back to his diocese by Pope John XV. He encouraged the evangelization of the Magyars, and founded the great abbey of Brevnov, but the opposition continued and he was at length forced into exile. He went as a missionary to Pomerania to preach the Gospel to the heathen Prussians, and it was there that he was martyred at the age of 41. See the articles in Wikipedia and the Catholic Encyclopaedia.

Red is the colour of fire and of blood. Liturgically, it is used to celebrate the fire of the Holy Spirit (for instance, at Pentecost) and the blood of the martyrs.