Detail of May

May (folio 3) from the Hours of Henry VIII, by Jean Poyet, c. 1500.

That is not an apron, but the lining of the gown that is shown as white over the green kirtle skirt. It may represent fur, or linen, or perhaps fine silk.

This color image from Morgan Library, The Hours of Henry VIII [Art] Retrieved March 6, 2006 from the World Wide Web: http://www.morganlibrary.org/exhibitions/po/html/h8intro_fr.html