They were martyred at Carthage in 203 during the persecution of Septimius Severus. With so many martyrs of the third and fourth centuries we have to say “they were martyred but nothing else is known about them.” That is not the case here. We have a detailed contemporary account of their arrest, trial, sufferings and martyrdom, written partly by the saints themselves and partly by an eye-witness. Devotion to them spread rapidly and they are mentioned in the Roman Canon of the Mass. See the articles in the Catholic Encyclopaedia and Wikipedia. The Wikipedia article contains links to the original account of their martyrdom.

St John Chrysostom (349 – 407) was elected Patriarch of Constantinople in 397. His sermons and writings did much to explain the Catholic faith and to encourage the living of the Christian life, and his eloquence earned him the surname “Chrystostom” (the Greek for “golden mouth”). The works of a number of other people were collected with St John’s own and travelled down the centuries with them. It is not now possible to discover who the original authors were.

Violet is a dark colour, ‘the gloomy cast of the mortified, denoting affliction and melancholy’. Liturgically, it is the colour of Advent and Lent, the seasons of penance and preparation.