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
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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
