Anansis is pretty well on the mark. All of us UK chaps and chappeses now have burgundy passports which state:
EUROPEAN UNION
UNITED KINGDOM OF
GREAT BRITAIN
AND NORTHERN IRELAND
(Royal coat of arms)
PASSPORT
For Bermuda, British Virgin Islands or St.Helena, your passport will be navy/black and state:
BRITISH PASSPORT
(Royal coat of arms)
TERRITORY NAME
For Anguilla, Cayman Islands, Montserrat, Turks & Caicos, Guernsey, Jersey or IoM - it's varying combinations of burgundy with/without 'European Union' etc etc.
Only others are British diplomatic passports or Queens messenger passports. Not likely to see those though unless you're; a) a diplomat/messenger or b) flying 1st class.