The fourth Sunday in Lent is sometimes called Laetare Sunday or Rose Sunday.
Laetare is the first word in the Introit, or opening, of the Latin Mass and means "rejoice." It's a Sunday when the church is called to joyful anticipation of Easter.
Though more common in the Catholic Church, some Episcopal churches observe Laetare Sunday using pink (or rose) vestments. Trinity does not currently have rose vestments, but will be pink flowers in the church to mark the day.