Purple

The colour most associated with wealth and luxury in the ancient world. The only source of the dye for fabric was a secretion—it turns purple only on exposure to air—from the gland of several species of a shellfish collectively known as Murex. The gland produces only a tiny amount of the raw material, making the dye an extremely high-value item. The city of Tyre was reputed to produce the best of such dyes in ancient times.

Lydia, one of Paul's first converts in the city of Philippi, was "a dealer in purple cloth" (Acts 16:12-15). Though a native of Thyatira she, nonetheless, had a house in Philippi to which she invited Paul and his companions to stay. She would have been a rather wealther lady, acquainted with the most wealthy circles of society in the city.