The North Dial of the Elizabeth Tower was unveiled on Thursday revealing the hands and numbers in its original Prussian blue colour.
The clock faces which looks out over Whitehall and the Embankment, is now fully visible after the surrounding scaffolding was removed and some tourists have been left surprised at the new blue hue.
The last time anyone would have seen a blue, rather than black, clock face on the north dial was before the 1930s.
The precise shade of blue to use was decided following extensive research into the Victorian tower's initial colour scheme, in consultation with Historic England.
The major restoration projection currently ongoing at the tower, designed by Sir Charles Barry and Augustus Welby Pugin in the 1850s, will be fully complete in 2021.
The landmark was silenced in August 2017 but the clock has since been occasionally restarted for national events, such as Christmas and Armistice Day.
The Elizabeth Tower, which houses the Great Clock and the Great Bell - known as Big Ben - last underwent major building in 1983-85.