The red and white rays in the Divine Mercy image have many layers of meaning.
When Jesus appeared to St. Faustina, she wrote that “slightly drawn aside at the breast, there were emanating two large rays, one red, the other pale” (Diary, 47).
This vision would become the basis of the Divine Mercy image, where red and white rays radiate from Jesus’ heart.
St. Faustina asked Jesus about these rays and he responded with the following message.
During prayer I heard these words within me: The two rays denote Blood and Water. The pale ray stands for the water that makes souls righteous. The red ray stands for the Blood which is the life of souls … These two rays issued forth from the very depths of My tender mercy when my agonized Heart was opened by a lance on the Cross.Diary, 299
First of all, these two rays correspond to the biblical account of Jesus’s passion and death.
[W]hen they came to Jesus and saw that he was already dead, they did not break his legs. But one of the soldiers pierced his side with a spear, and at once there came out blood and water.John 19:33-34
Secondly, it is believed that Jesus was referring to the sacrament of Baptism when highlighting the “water that makes souls righteous.”
The red blood is often seen as a symbol of Jesus’s sacrifice, as well as the sacrament of the Eucharist.
Both sacraments are often described as having been “born from Jesus’ side” on the cross.
Red is also frequently a reminder of Jesus’ intense love for humanity, and a symbol of Jesus’ Divine Mercy.
The Divine Mercy image has much symbolism and provides a beautiful encapsulation of the Gospel message.