He was born in Italy of a noble family. He became a soldier but his taste for gambling and riotous living eventually lost him everything. At the age of 25 he converted as the result of hearing a sermon. He twice tried to join the Capuchin friars but was rejected because of his poor health. Having had experience of hospitals from the inside, he determined to improve them, and he devoted the rest of his life to the care of the sick. He offered himself to the hospital of San Giacomo in Rome and eventually became its bursar. Hospitals were as filthy, and hospital staff as brutal and inadequate, then as they are in many places today. He introduced many reforms and founded a congregation of priests and lay brothers, the Servants of the Sick (later known as the Camillians) to serve the sick both spiritually and physically. He was ordained priest in 1584. He resigned as head of his congregation in 1607 but continued to look after and visit the sick almost until the day of his death.

Ambrose was born in Trier (now in Germany) between 337 and 340, to a Roman family: his father was praetorian prefect of Gaul. Ambrose was educated at Rome and embarked on the standard cursus honorum of Roman advocates and administrators, at Sirmium, the capital of Illyria. In about 372 he was made prefect of Liguria and Emilia, whose capital was Milan.

The theological virtue of hope is symbolized by the colour green, just as the burning fire of love is symbolized by red. Green is the colour of growing things, and hope, like them, is always new and always fresh. Liturgically, green is the colour of Ordinary Time, the orderly sequence of weeks through the year, a season in which we are being neither single-mindedly penitent (in purple) nor overwhelmingly joyful (in white).