false colours

British  

plural noun

1. a flag to which one is not entitled, flown esp in order to deceive

   the ship was sailing under false colours

2. an assumed or misleading name or guise

   to trade under false colours

---

Example Sentences

The new photographs include images in false colours that clearly show the shape of Carn Glas.

From BBC • Sep. 26, 2023

We came here somewhat under false colours, to try and find out about this murder, and in the hope we might discover some proofs of Captain Mervyn's innocence.

From The Curse of Carne's Hold A Tale of Adventure by Henty, G. A. (George Alfred)

I'll win this woman under no false colours.

From The Man Who Rose Again by Hocking, Joseph

A veritable army had landed at Killala under false colours, flying a mendacious Union Jack: veterans to the number of twelve hundred, who had fought in Italy under Napoleon.

From My Lords of Strogue Vol. III, (of III) A Chronicle of Ireland, from the Convention to the Union by Wingfield, Lewis

Goeze chose to consider that Lessing was sailing under false colours, that the fragments were his own composition, and that he was undermining the national faith.

From The Dramatic Works of G. E. Lessing Miss Sara Sampson, Philotas, Emilia Galotti, Nathan the Wise by Lessing, Gotthold Ephraim