I thought we’d look at the various rites of Penance in detail. I don’t think the options are as deeply plumbed as they are in Marriage, so there may be a surprise or two for penitent, confessor, or liturgist.
The Rite offers prime choices for prayers and readings, then refers to subsequent chapters and appendices for additional options.
Here are the texts for those interesting in “saying the black, doing the red,” picking up where we left off before Christmas and starting with form I. Of course, the “red” is plain purple, the “black” is bold print:
CHAPTER I RITE FOR RECONCILIATION OF INDIVIDUAL PENITENTS RECEPTION OF THE PENITENT
41. When the penitent comes to confess his sins, the priest welcomes him warmly and greets him with kindness.
42. Then the penitent makes the sign of the cross which the priest may make also.
In the name of the Father, and of the Son, and of the Holy Spirit. Amen.
The priest invites the penitent to have trust in God, in these or similar words:
May God, who has enlightened every heart, help you to know your sins and trust in his mercy.
The penitent answers:
Amen.
Other forms of reception of the penitent may be chosen from nos. 67-71.
INVITATION TO TRUST IN GOD
67. Ezekiel 33:11
The Lord does not wish the sinner to die but to turn back to him and live. Come before him with trust in his mercy.
68. Luke 5:32
May the Lord Jesus welcome you. He came to call sinners, not the just. Have confidence in him.
69.
May the grace of the Holy Spirit fill your heart with light, that you may confess your sins with loving trust and come to know that God is merciful.
70.
May the Lord be in your heart and help you to confess your sins with true sorrow.
71. 1 John 2:1-2
If you have sinned, do not lose heart. We have Jesus Christ to plead for us with the Father: he is the Holy One, the atonement for our sins and for the sins of the whole world.
Confessors and penitents are especially encouraged to chime in on this. Do you use “the invitation to trust in God?” The rubrics leave the exact wording open to the confessor. Do confessors use them verbatim? Adapt them more conversationally? Use other Scriptures? Or omit them entirely?
Catholic Sensibility 
Since I can remember, I’ve been saying this to penitents: “May the Lord be in your heart and on your lips to help you make a good confession.”
I don’t ever recall a penitent responding, “Amen” – or responding with anything except, “Bless me, Father, for I have sinned…”
I hear a lot of Spanish confessions, which generally start “Ave Maria Purisima… en gracias de Dios concebida.” I’m guessing that’s a pre-V2 formula.