Lit., became different. Luke avoids Matthew's word, μεταμορφώθη, was metamorphosed. He was writing for Greek readers, to whom that word represented the transformations of heathen deities into other forms. See, for instance, the story of the capture of Proteus by Menelaus, in the fourth book of Homer's “Odyssey.” See on Mat 17:2.
White (λευκὸς)
In classical Greek very indefinite as an expression of color; being used, not only of the whiteness of the snow, but of gray dust. Its original sense is clear. All three evangelists use the word, but combined with different terms. Thus, Matthew, as the light. Mark, στίλβοντα, glistering (see on Mar 9:3). Luke, ἐξαστράπτων (only here in New Testament), flashing as with the brilliance of lightning. Rev., dazzling.