The grey Voyager jet is to get a £900,000 red, white and blue paint job as part of a pre-planned overhaul.
The Union flag-style rebrand will allow the RAF Voyager to continue to participate in military work, according to Number 10.
On Wednesday, the Prime Minister’s official spokesman said: “The RAF Voyager used by the royal family and the Prime Minister is currently in Cambridgeshire for pre-planned repainting.
“This will mean that the plane can better represent the UK around the world with national branding, similar to many other leaders’ planes, while also retaining its military air-to-air refuelling capability.”
The spokesman defended the £900,000 cost, telling reporters: “That incorporates the cost of creating a design that will promote the UK around the world without compromising the plane’s vital military role.
“At every stage we have worked to ensure value for money for the UK taxpayer and all of the work has been undertaken in the UK, directly benefiting British suppliers.”
Mr Johnson has previously questioned why the plane is grey.
As foreign secretary he said would like to have a “Brexit plane” to help him travel the world and promote the Government’s vision of global Britain.
He complained in 2018 that the RAF Voyager jet, which is shared by the Prime Minister, senior Cabinet members and the royal family, “never seems to be available”.