[HarleyD]

I don't think the color blue in classical paintings had to do with realism. I believe it represented something (purity, holiness, etc.). It has been many years since I've studied art. Perhaps an art major would know.

It's not important. This looks like a neoclassical painting to me and I thought most neoclassical painters painted Mary's robed in blue. (see below some examples)

[old and tired]

A poem all my kids learned at a very early age:

Lovely Lady, dressed in blue,
Teach me how to pray.
God was once your little boy -
Tell me what to say

[sassbox]

I'm no art major, but I took alot of art history classes when I studied in Rome in college. Portraying Mary in blue goes back to medieval times - in first millenium mosaics in Rome, blue and extremely expensive lapis lazuli was reserved for depicting the Virgin's robe. It definitely must represent purity or some other virtue, not a realistic depiction of what Mary wore.