The historicity and actual physical appearance of Mary and other figures is rather unimportant. Isaiah 53:2 foretells of the Messiah, “He grew up like a sapling before him, like a shoot from the parched earth; He had no majestic bearing to catch our eye, no beauty to draw us to him.” yet Christ is invariably portrayed as handsome, and usually imposing or at least very charismatic. His inner beauty is evident in the Gospels, of course, and this reflects on the Blessed Virgin Mary, who sang the sublime canticle, “Magnificat”.
1 Cor 9:19-23 reads, “Although I am free in regard to all, I have made myself a slave to all so as to win over as many as possible. To the Jews I became like a Jew to win over Jews; to those under the law I became like one under the law—though I myself am not under the law—to win over those under the law. To those outside the law I became like one outside the law—though I am not outside God’s law but within the law of Christ—to win over those outside the law. To the weak I became weak, to win over the weak. I have become all things to all, to save at least some. All this I do for the sake of the gospel, so that I too may have a share in it.”
The Old Covenant was between Israel and a tribal God, but when Christ came to announce the Good News, he sent apostles to every corner of the Earth, to Jews and Gentiles alike. The Catholic principle of inculturation redounds to the idea of the universality of the Gospel message. You have all heard the saying that we should “meet people where they are.” The apparitions and renditions of Mary assuming different ethnicities follow from that ideal.
We can all find saints and heroes who look like us, who act like us, who feel natural to us. The universality of Mary’s patronage and motherhood naturally lends itself to a fluid appearance. She is not merely the mother of a Jewish carpenter in 1st-century Judea, she is the Mother of God and the Queen of Heaven!