Sentence:  While waiting for others to arrive, Margaret Scott-Stewart, a big, friendly woman of 55 in a tartan tunic and <WSD>blue bonnet</WSD>, smokes Royals and sings 'Charlie Is My Darling'. 
Meaning of the word marked with <WSD> tags:  A traditional flat Scottish hat made of blue wool; a blue tam-o'-shanter. (from 16th c.)