On this day (20 November) in 1880 as Newton Heath L&Y Railway Manchester United played their earliest known game. It was against Bolton Wanderers 2nd team and United lost 6-0. In the years that have followed some have claimed they wore green and gold at this game but the contemporary references given do not say anything of the sort.
It is still repeated often that a newspaper report in the Bolton Evening News mentioned the colours of green and gold were worn for Newton Heath’s first reported match. The origin of this is unclear but the Manchester United Pictorial History and Club Record (Charles Zahra, Joseph Muscat, Iain McCartney and Keith Mellor; Nottingham: Temple Press, 1986) specifically refers to the match report on page 11 as being published on 24 November 1880 and implies it stated the team colours. It also suggests that Bolton wore scarlet shirts.
My research over the decades has included a review of every Bolton newspaper for that period and I did discover a match report in the Bolton Evening News on the date mentioned in the above book but this did not include any reference to the colours worn. This is actually the report that gets quoted. You can see there’s no mention of colours:

Like so many football clubs the early history of Newton Heath has lots of myths associated with it. The facts are that at the railway works in Newton Heath various sporting activities were established during the 1870s. In 1922 Herbert Dale, a railway worker who played football for a decade from the formation of what became Newton Heath, was asked how football became established at the works. He explained that the club when initially formed had been a cricket team (suggesting it was established in 1878), and that after some time a member of the committee bought a football from a shop on Market Street in the city centre. This appears to be in 1880 and, according to Dale, the instigator of the club was Sam Black and that the original colours were red and white quartered shirts (NOT green and gold; quartered shirts meant 2 panels on front and 2 on back with a red and a white panel on both the front and the back). Those colours may surprise some but I do provide references and explain more in a book The Emergence of Footballing Cultures: Manchester 1840-1919 published by Manchester University Press. In that I talk about all the early clubs of the Manchester area such as Hulme Athenaeum, Manchester Association and Hurst.

Black was seventeen when the club played its earliest known game on 20 November 1880 and his age then seems consistent with others, such as those at St Mark’s (Manchester City) who are known to have played in November 1880.
The was a Sportsman’s Yearbook for 1880 produced which the Newton Heath club was mentioned in. It appeared in both the cricket and football sections. Here are the details published in the cricket section:

You’ll notice mention there of the cricket whites/kit to be worn: white with a blue cord. Typically, this is believed to mean ‘white cricket shirts and trousers’ with a blue cord as belt (to differentiate between opponents). Some cricket clubs wore different coloured belts/cords; some wore specific caps with their whites and some wore badges (or even different colours).
In that same yearbook the following appeared in the football section (back then a football section had rugby and association football clubs alongside each other):

You’ll notice the details are simply a repeat of the cricket section and it may well be that the club had decided to be listed in both sections without thinking specifically about football, or it could even be that it was a mistake to publish in both sections. For me it does seem that having the club’s details in both sections was deliberate, afterall it says the club is all year around and not specific to the cricket or football/rugby season. But I don’t believe the colours can be trusted for the association football team, especially as Dale talks of red and white being the club’s earliest football colours. Whatever is true it is important to recognise that to date no contemporary evidence has been found saying the club wore green and gold when they played their earliest games. They did wear those colours at times later on though.
Newton Heath reformed as Manchester United in 1902, winning the club’s first major trophy in 1908 (the League).
Incidentally Bolton Wanderers’ first team beat Irwell Spring (Bacup) 7-1 in the Lancashire Cup on the same day as the earliest known game for the Heathens. A good day all round for the Wanderers it seems.
For those wondering the earliest known MCFC game took place one week earlier (St Mark’s v Macclesfield Baptists).