It’s a classic button-push issue (like bent bananas etc), mostly cooked-up by Priti Patel (HM’s Home Secretary, previously Secretary of State for International Development).
Here’s the Gov’t statement: note the weasel words.
Iconic blue passports return next month - GOV.UK (www.gov.uk)
“Britons will be able to travel with a blue passport when the traditional colour returns for the first time in almost 30 years.”
“The distinctive blue cover will be re-introduced now the UK has left the EU, and will replace burgundy passports which were gradually rolled out from 1988.”
"Leaving the European Union gave us a unique opportunity to restore our national identity and forge a new path in the world.
By returning to the iconic blue and gold design, the British passport will once again be entwined with our national identity and I cannot wait to travel on one."
"The blue cover is a return to the original appearance of the British passport, with the colour first used in 1921.
It remained the colour of choice until the UK joined the EU when a change to burgundy was agreed and adopted."
But this nowhere says that the UK was compelled to change its passport colour/color anytime between joining on 1 January 1973 and leaving 47 years later. That’s because it wasn’t!
For some essentially right-wing, pro-Brexit comments, look at the Daily Express.
Blue passports return NEXT MONTH in huge step to restore national identity after Brexit | UK | News | Express.co.uk
"The burgundy document approved by Brussels caused upset among Eurosceptics when it was introduced in 1988.
Brussels later floated plans to remove the Queen’s crest to make it more European and to end use of the phrase “Her Britannic Majesty” in the documents."
But this was a proposal made by members of the EU, the club we had joined. And we, and other members would have none of it.
So: it’s another Brexit lie.