When the Virgin Mary is portrayed wearing blue, it is said to be because the color is associated with nature, royalty and peace. She is sometimes portrayed wearing red or other colors, depending on the artist's impression of the Virgin Mary and the desires of the person commissioning the work or art.
In some older works, the Virgin Mary is portrayed wearing darker blue colors. She has also been shown wearing red, white and gold. Some of the gowns and mantles she is shown wearing in various works are based on her appearances to people on Earth.
Our Lady of Lourdes appeared in 1858 to Bernadette wearing a simple white gown and mantle with a blue sash. Our Lady of Fatima appeared in 1917 to children wearing a white gown and mantle that had gold trim and a crown. Our Lady of Guadalupe appeared in 1531 wearing a blue mantle with stars and a rose gown.
Even those colors might not be historically accurate. When Mary was living, her clothing probably wouldn't have had much color at all. Blue and purple colors were made then by using plants to make dyes. The plants for blues and purples were rare, so those colors were reserved for royalty and the wealthy.