blue, v.¹ — Green’s Dictionary of Slang

blue v.¹

[the colouring (actually dark red) of one’s complexion]

to blush.

1709		R. Steele Tatler No. 71 166: If a Virgin blushes, we no longer cry she Blues.
1719		H. Misson Memoirs of Travels over England 169: King Edward III, who was deeply in love with the Countess of Salisbury, was very forward to take up a (blue) Garter which happened to drop from the Lady’s Leg while she was dancing at a Ball: This action set many of the Company a Laughing, which very blew’d the Countess.