For those of you who don't know, it's usually customary to wear black at a funeral as a show of mourning and respect for the deceased.
So you would perhaps have thought that those visiting Vatican City for Pope Francis' funeral at the weekend would follow this tradition.
However, US President Donald Trump has been widely criticised after showing up in a blue suit, while his wife Melania wore all black, despite it being her 55th birthday.
The 78-year-old found time before the service began to sit down with President Volodymyr Zelenskyy, a few months after their explosive chat at the White House.
However, this talk seems to have been far more productive, even despite the Ukrainian once again choosing not to wear a suit, as a ceasefire between Russia and Ukraine was confirmed for May, on Monday morning (28 April).
However, users on X were quick to criticise the US leader for his attire and accuse him of ‘breaking the dress code’, which seemed to be where some drew the line after his chaotic first few months back in office.
One user questioned: "Any reason why Donald Trump is in a blue suit and not wearing traditional black for a funeral?"
Another said: "Watching the funeral on BBC News. Trump is in a blue suit when everyone else is in black. No class."
Someone else pointed out: "Why is Trump wearing a blue suit while everyone else is in black? No respect."
In Trump's defence, which isn't something I say often, a few other attendees, including Prince William and Indian President Droupadi Murmu also wore blue, which suggests that there was a good reason why they opted out of wearing black.
Prince William was also in blue (Antonio Masiello/Getty Images) Although Trump may well have been disappointed at being handed a 'third-tier seat' at the funeral last weekend, following the Pope's passing on Easter Monday, it seems as if he wasn't actually breaking any rules when it came to his outfit of choice.
It is suggested that while Catholics have firm guidelines when it comes to funeral attire, other faiths do not impose this as strictly. So Trump, who is a non-denominational Christian, Prince William who belongs to the Church of England and President Murmu, who is Hindu, may have all been wearing blue as a sign of their non-Catholic faith.
Droupadi Murmu next to Volodymyr Zelenskyy (Jakub Porzycki/NurPhoto via Getty Images) According to Sky News, the dress code for the Pope's funeral expected men to wear a dark suit with a black tie, 'and a button of the same colour on the left lapel of the jacket, where only Vatican honours can be placed'. White shirts were also allowed.
Trump certainly likes to do things his own way, but it seems as if he has got himself a valid excuse this time at least.