'BLUE' was the designation of Allied convoys (together with a numerical suffix) plying the route from Port Said, Egypt, to Gibraltar (September/November 1939).

The first of these convoys was BLUE.1 between 9 and 19 September 1939, and this comprised 20 British merchant ships in the form of the 8,299-ton Abbeydale, 8,402-ton Aldersdale, 6,993-ton British Engineer, 7,138-ton British Science, 10,304-ton Calchas, 8,062-ton Carelia, 6,589-ton City of Adelaide, 5,861-ton City of Dunkirk, 11,080-ton Dilwara, 4,212-ton Frances Massey, 3,297-ton Kioto, 14,182-ton Largs Bay, 11,851-ton Llangibby Castle, 7,998-ton Macharda, 6,690-ton Mahratta, 8,181-ton Maja, 6,677-ton Makalla, 7,506-ton Memnon, 1,960-ton Palestinian Price, and 6,148-ton Stentor.

This set the pattern for the following convoys, which were also unescorted and ended with the BLUE.6 convoy between 26 October and 6 November with eight British vessels in the form of the 5,920-ton Benwyvis, 6,098-ton British Lord, 5,890-ton British Petrol, 5,576-ton British Sailor, 6,991-ton British Statesman, 4,672-ton Clan Macinnes, 4,500-ton Clan Maciver, and 4,937-ton Queen Anne.