Interesting picture. I thought Mary was always pictured in blue.
There are no hard and fast rules (of which I know). I suppose it depends on the style of the artist. The above painting was done by the Spaniard Diego Velasquez.
In the picture of Our Lady of Guadlalupe she is pictured in a hue of orange.
during her earthly life she probably never wore anything blue, since she was poor and dyes were expensive. It is a lovely color though!