There's an ongoing debate about what colour the new passport really is.
The Home Office has released pictures of the post-Brexit passport, describing it as a return to the "iconic blue" passport.
Blue passports were used before 1988, before the government changed them to red.
But colour science experts aren't convinced that it is truly blue, in fact they think it leans closer to black - and social media users agree with them.
Speaking to the BBC, Stephen Westland, professor of colour science and technology at the University of Leeds said: "I'd say it's black.
"If most people looked at this, they'd say it's black."
He adds that describing colours in terms of a name can often be imprecise, because people will always have their own opinions.
People have taken to Twitter to debate what colour the new passport really is.
One person wrote a post that reads: "There is some right Emperors New Clothes going on with this 'blue' passport that actually looks black."
While another Twitter user says: "Can we stop fighting about whether the passports are blue or black, the word Navy exists for a reason."
Craig Burston, a senior lecturer in graphic design at the London College of Communication told the BBC that he doens't think that blue is the "dominant colour" of the new passport.
Suggesting it leads towards a charcoal colour, with a hint of blue.
Meanwhile other Twitter users are urging people to concentrate on what the passport represents, as opposed to its colour.
"It's also a shame no one mentions they could've been black, sorry blue under the EU anyway colour was never a rule. This whole pad port colour thing is just Tory Anti eu BS," tweeted one user.
Another person commented on this tweet, saying: "Yeah, that fact annoys me, especially with headlines like 'finally the UK return to "iconic" blue passports'. We chose to change colour as a sign of unity and didn't have to leave the EU to change it! #bluepassport #couldvechangedanytime"
