This unit was repainted green in 1986 or 1987 (I photographed it in green in September 1987).
It was withdrawn by the end of 1988 - it doesn't appear in the 1989 edition of 'Locomotives & Coaching Stock' by Platform 5 Publishing, which was correct as of 1st January 1989.
DMU coaches numbered 50xxx and 56xxx were renumbered 53xxx and 54xxx respectively in 1983 and 1984.
Other green units around that time were class 108 53964 + 54247 and class 127 parcels unit 55966 + 55967.
Two 'one off' liveries in the mid 1980s were class 117 51368 + 59520 + 51410 which received GWR chocolate & cream, and class 104 53424 + 53434 in red and white 'Mexican Bean' livery.