[…] again Laughed the blue eyes without a stain. (44-45)
"Stain" is usually a metaphor for sin (like the bloodstains that Lady Macbeth can't get off her hands), but it's not clear what the metaphor of the "stain" is doing here. Is the speaker suggesting that, now that Porphyria is dead, the "stain" of her sins is gone? Or is he relieved to find that there is no visible "stain" in her eyes to mark his sin of murdering her?