Colours on drinking vessel (6)

I believe the answer is:

flagon

'drinking vessel' is the definition.
(I've seen this before)

'colours on' is the wordplay.
'colours' becomes 'flag' (colour can mean a national flag).
'flag'+'on'='FLAGON'

(Other definitions for flagon that I've seen before include "Large rounded bottle, may contain cider" , "Large wine-bottle, jug" , "Large wine vessel" , "Large vessel with a handle and spout" , "Snow White companion" .)

I've seen this clue in The Times.

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