E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
applied to troops.
The Oxford Blues. The Royal Horse Guards were so called in 1690, from the Earl of Oxford their commander and the blue facings. Wellington, in one of his despatches, writes:I have been appointed colonel of the Blues.
It was also known as the Blue Guards during the campaign in Flanders (17421745).Trimen: Regiments of the British Army.