England, Wales, Scotland and Northern Ireland will be classed as single regions, rather than broken down at local authority and lower tier levels as they have been previously.
Scotland and Northern Ireland will be amber from 28 May, while England and Wales will be classed green, along with Guernsey and the Isle of Man.
However, 15 areas which have seen rising cases and concerns over the Indian variant have been classified as red, including ten in England and five in Scotland. These include mostly areas in the North of England, such as Bolton, and the Scottish Central Belt, including Glasgow.
The government said there would be at least 48 hours' notice before emergency brakes were put in place.
Updates to Common Travel Area classifications will be announced on a weekly basis, the government has said.
International travel also opens from Friday, with Jersey's government mirroring the UK's classifications, meaning places such as Portugal will be classed as green. However, jurisdictions whichJersey has direct connections with, including France, the Republic of Ireland and Madeira, will be assessed on a Jersey government basis.This includes a regional approach for France and Ireland.