Flag of Anguilla (adopted on 30 May 1990) - RGB colours, 1:2 dimensions and construction details based partly on the templates: Flag of Anguilla – A Brief History
It is created by John C Meuser, and is part of openclipart.org
This work created by the United Kingdom Government is in the public domain.
This is because it is one of the following:

It is a photograph taken prior to 1 June 1957; or
It was published prior to 1974; or
It is an artistic work other than a photograph or engraving (e.g. a painting) which was created prior to 1974.HMSO has declared that the expiry of Crown Copyrights applies worldwide (ref: HMSO Email Reply)More information.  

See also Copyright and Crown copyright artistic works.