The most-watched Premier League game in British history between Liverpool and Manchester United was actually un-watchable for hundreds of thousands of viewers, who are colour blind.
Almost five million football fans tuned in, but an estimated 300,000 of them struggled to tell one team from the other.
Supporters who experience 'colour vision deficiency' were horrified to discover United had chosen to wear their away strip for the match at Anfield, which is 'earth green', while Liverpool wore their traditional red kit.
The shades of red and green worn by Liverpool and Manchester United were indistinguishable to colour blind people in the most watched televised Premier League game in Britain
The 'earth green' of United's away strip is a similar shade to Liverpool's red kit
Green and red, particularly in darker shades, are indistinguishable for many colour-blind people, who gave up on the contest long before the end because they simply could not see who was who, resulting in hundreds of complaints.
'I ended up switching it off,' said Kieran Maguire, a football finance expert, who is colour blind. 'It was too baffling. Where the colours are broadly of the same degree of light or shade then, as a colour-blind person, you have a problem.
'This was the biggest match of the season and generated record viewing figures and in the end, I spent my time swearing at the TV because I could not tell who was who.'
The potential incompatibility of red and green is well known in football. The FA has produced a video to highlight the difficulty colour blind people have distinguishing the two colours.
These simulated images produced by UEFA, show how a colour blind person can find it hard to distinguish between red and green strips of a similar lightness or darkness
Red and green can be hard for colour blind people to tell apart, particularly if a similar shade
And the Premier League has developed a 'colour blind friendly flag'’ which identifies the best kit combinations for people who are colour blind and uses a 'bespoke online software tool' to test whether strips should be worn together.
Clubs submit their kit choices to the league ahead of matches for approval.
In this case, Sportsmail understands the Premier League indicated in the days before the game that there was a problem and United agreed to change the socks from green to white to address the issue.
The club believed this would solve the problem, but in the event, while it helped, it was not enough and viewers still struggled to tell the teams apart. United are now aware of the issue and have responded directly to complainants, including Maguire, explaining what happened.
United's Bruno Fernandes is a colour blindness ambassador for the Portuguese FA
Sportsmail understands they accept the change to the socks was not enough and would make further changes in the future.
Embarrassingly, United's star midfielder, Bruno Fernandes, is a colour blindness amabassador for the Portuguese FA.
Liverpool visit Manchester United this weekend in the fourth round of the FA Cup with the Merseysiders expected to wear their teal away kit. It is understood this kit has been tested against United’s red strip and the lighter tone means it will be compatible.
In Britain, one in 12 men and one in 200 women are colour blind, with three million people affected in total.
During the Liverpool-United game, hundreds of fans took to Twitter to voice their anger over the strip selection.
Long shots and busy scenes were particularly difficult for colour blind people to decipher
Colour blindness affects around three million people in Britain and it is a lot more common in men than women.
One in 12 men, compared to one in 200 women, suffer from colour vision deficiency.
Usually, colour blindness is a genetic condition, although some people become colour blind as a result of other diseases such as diabetes and multiple sclerosis or they acquire the condition over time due to ageing.
The most common form of the condition is known as ‘red/green' colour blindness and although this a familiar term, there are different types and severities of it.
Being red/green colour blind doesn’t mean people with it mix up red and green only, it means they can mix colours which have some red or green as part of the whole colour.
So someone with red/green colour blindness will probably confuse blue and purple because they can’t ‘see’ the red element of the colour purple.
Disappointed fan, Mark Abbott tweeted: '@skysports have introduced snicko, ball tracking, player cam and all manner of innovations to, presumably, make watching sport better on their platforms.
'But its beyond their whit to insist one club wears a light strip and the other a dark one? Ok. Its near impossible to fix... '
Chris Hope tweeted: 'Virtually indistinguishable to me. Absolute joke.'
Hope and Abbott were not alone is making their disappointment known.
'Sunday was the most kit clash complaints we have ever had,' Kathryn Albany-Ward, CEO of Colour Blindness Awareness told ESPN. 'We had hundreds.'
"It is a really common problem, and it is a big problem because of the amount of people affected.'
This is not the only match to have suffered a kit clash in the Premier League this season.
The game between Southampton and Sheffield United also sparked anger when they lined up in red and green combinations.
In America, the NFL had to change their approach to kits after a match between the all-red Buffalo Bills and all-green New York Jets in 2014, which could not be told apart by 14 million colour blind people, who then protested vociferously.
"The NFL had to change their kit regulations to make sure that it didn't happen again.
"I think they do need to rise up to a large extent in the UK. People are aware of it, but they don't retain the information long enough to do something about it.
The match between Southampton and Sheffield United also caused viewing problems
The Premier League uses software to test the compatability of team kits before games
"If a major broadcaster was to take this on, and present what it is like to be colour-blind and watch a game to the right people. I think that would be great.
"The Premier League does act, and they do notify the clubs, as they know when these clashes will happen. I know because I was in touch with them today.
"They told United of this issue and United suggested a solution, but what they decided was not sufficient."
The Premier League says it works with clubs on selecting the best kit for each match.
'The Premier League has a detailed process in place to ensure that the kits selected for both teams in all fixtures are identifiably different colours and to ascertain the best possible kit combination for each match,' said a spokesman.