Most people don’t know that The Pieta was housed in the Old St Peter’s, where lighting would fall down onto the artwork from above, rather than shining upwards onto it as we see it today
That means Michelangelo originally sculpted this with the intention of Mary’s face having shadows over it and Christ’s body being illuminated in contrast
The symbolism would be something like her, like us, being somewhere in between sorrow for the Crucified Christ and hopeful in His Resurrection
It’s interesting how subtle changes, even just the lighting, changes the meaning we take away from art