She had seen it in the Consort, in the West March.
The Consort's eyes turn sky blue in "Cast in Sorrow" after Kaylin turned the Nightmares of Alsanis into eagles/dreams.
But she's also seen sky blue in Nightshade's eyes twice. First in the past in "Cast in Silence" while in the Tower soon-to-be-of Tiamaris, on dragonback flying up to the aerie. Then in "Cast in Chaos" right after talking about what happened in the tower in the past and right before he kissed her.
