The navy version of the flag is seen on display in September
President Emmanuel Macron has switched to using a darker navy blue on the official French flag, replacing the previous brighter shade, officials have told local media.
The move saw flags in the new hue hoisted on the presidential palace last year without any accompanying fanfare.
Mr Macron wanted to bring back the navy blue flag, a symbol of the French Revolution, Europe 1 said.
However, both the darker and lighter flags have been in use for decades.
France's navy and many official buildings around the country have always used the navy blue shade.
But in 1976 under President Giscard d'Estaing, the French state introduced a brighter blue on the tricolour to match the blue on the flag of Europe.
That decision was partly an aesthetic one, Europe 1 reports, because the French and European flags flew next to each other in so many locations.
The Élysée Palace has not publicly announced its change in flags, and no orders have been given for other institutions to do the same.
There was reportedly some disagreement over Mr Macron's change back to navy blue, with some arguing the new shade was ugly and would clash with the EU flag, and others nostalgic for the pre-1976 version.
However, all concerned insist that the colour change should not be interpreted as an anti-EU gesture, Europe 1 reports.
France is due to take on the rotating EU presidency in January.
Mr Macron also faces a presidential election in April next year.