F1's governing body may revisit the rule banning drivers from using different helmet liveries.
There was controversy at Sochi when local driver Daniil Kvyat was prevented from wearing a special helmet for his home Russian GP.
The ban fell after the FIA told Toro Rosso that Kvyat had already used his allowed 'one off' special helmet at Monza.
However, Sebastian Vettel gets around the rule by making minor tweaks at almost every race.
And Max Verstappen used a special yellow helmet in Austria, and then a special all-orange helmet at Spa.
Asked why the FIA chose only to ban Kvyat from running a second special livery, race director Michael Masi said: "Chose is the wrong word.
"We were asked whether the new helmet would be considered substantially similar to the main version, which is what the regulation is, and our answer was no."
Masi said he isn't sure if the regulation will now be looked at again, and admitted that "not all" teams and drivers consult with the FIA before making livery changes.
When pressed about the three substantially different helmets used by Verstappen this year, Masi added: "To be honest, I'll have to look at that again before commenting."
