Lent : Purple is indicated, as the stark color of repentance and solemnity.
Sunday of the Passion : Scarlet is the preferred color of this first day of Holy Week, as it suggests the deep color of blood.
Days of Holy Week : Scarlet or purple may be used for Monday, Tuesday, and Wednesday of Holy Week.
Κύριε, ἐλέησον might be the only Greek phrase you know. Ever wonder why?