Fairy eyes come in five colors: blue, lavender, silver, gold, and green. Petal was one of the few whose eyes were all these colors.
Blue denotes humor, a spirit of mischief and merriment, while lavender eyes indicate tranquility, a satisfaction and peace with one's sphere. Silver is for wisdom, an intuitive feel for the right thing, while gold is for an affinity for beauty and music. And green is for love, of the sort that is selfless and giving and enduring.
And so Petal decided to keep hers green while she was married. At least, when others could see her.