Following a rule introduced in 2015, F1 drivers had been forbidden from changing their helmet colours throughout the campaign.

Teams and F1 chiefs felt that the practice of some drivers - like Sebastian Vettel - of switching helmet colours at each race made it difficult for fans to recognise them.

Drivers initially accepted the situation but more recently have begun lobbying the FIA to allow a little leeway.

That came ahead of the Monaco Grand Prix, with the FIA agreeing that each driver would be allowed one special livery each season.

An FIA spokesman said: "We have given each driver one 'joker' which will allow them to use a different helmet design at one race, e.g. his home race."

A number of drivers have used that opportunity for different colours in Monaco this weekend - including Lewis Hamilton and Felipe Massa.

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