Early Colours, and Type (Europe)
Primitive pony stock
Brown to dun, in various shades, is often mentioned as a common "primitive" equine colour range.
There is wide scope to guess at the colours of any imported stock that may have mixed with the natives so far back as the Roman occupation. There are suggestions in various books that the early stock was "dark", in line with the modern Fell breed colours. We do not have any direct evidence of what colour the UK pony stock may have been at such an early date but there has been research into the colours of European horses in prehistory using DNA from Swedish Iron Age samples: the colours there were mainly bay, chestnut and black.
Foreign colour range
Virgil, the Roman poet writing about agriculture around 29 BC, liked bays and greys best and disliked white or yellow horses. White horses were used as sacred diviners by the northern Germanic tribes, and the county of Kent, one of the areas that they settled in Britain, still has a white horse as its symbol. Palladius in the 4th Century AD described the horse colours that he knew: "chestnut, golden, albino, bay, brown, fawn, yellowish, checkered [spotted? dappled?], dead white, piebald, glistening white, black, dark. Of less value... black mixed with albino or chestnut, gray with any other colour, dappled, spotted, mouse-colour, or duskier." (ref.) Britain was part of the civilised world and was open to trade as well as to military movements. A wide range of horse colours was available to influence its stock. But literary evidence to show those colours is sadly lacking.
The only local reference I have found that is even vaguely related to the Fell's homeland comes from Taliesin, the 6th C Welsh bard. One translation says that King Arthur took "creamy" or "pale" horses from the area of the Wall (Dent). But even this is open to dispute, as the Old Welsh word translated as "wall" may mean not mean Hadrian's Wall in the northern border country.
Exotic colours do not persist
What is notable is that if there were exotic colours, they did not seem to persist in Britain: it is mainly brown, bay, dun, black, grey and occasionally chestnut, with markings such as white socks, stars and blazes, that seem to have been recorded in later English lists and illustrations.
Modern Fell Colours
From 1898 until the 1960s, "brown" or dark bay Fell ponies were about as common as black ones (see 1913 colours of foals). Small numbers of greys were registered in the early stud books. Black did not become predominant in the Fell breed until the second half of the 20th century. 4 chestnut Fells were registered prior to the First World War; there were two or three pied or skewbalds; and occasional roans and duns persisted into the later 20th C. In 1969 the Fell Pony Society News reported that blue and red roan ponies were still occasionally foaled in Mr W Winder's herd at Caldbeck; 8241 Mountain Gipsy by Mountain Jester 1409, was red roan. She threw blue or red roan foals although put to a black stallion. Solid coloured ponies, bay or black, occasionally show white flecking or "ticking", with single white hairs showing on the flanks and/or tail head, which is unrelated to ageing.
Some of the Fell pony men in the 1980s and 1990s preferred a dark brown pony (almost black with tan muzzle) because they said it could not be beaten for hardiness. "Them broon 'uns are bad t'kill on t'fell!"
Liver chestnut Fells have occasionally been bred in more recent times, but not registered. Since 2006 they may be registered in Section X of the Stud Book, for ponies that are by pedigree parents but do not conform to the breed standard.
When you compare modern Fells with photographs of their late 19th Century predecessors you can see they are now more heavily feathered around the legs and feet, and have less steeply sloped quarters and shoulders. Breeders say that some modern ponies show more bone but they are reserved about its quality; older ponies are said to have had flatter bone. Even under heavy feather it feels clean and flint-hard. Roman ponies however are unlikely to have been as big as the modern Fell. Even those bred in the early 20th C were often smaller, in relation to their handlers in photographs, than the modern ponies are.
Today's "show" Fells often look more thick in the body than older types, but this is generally only a difference of fat covering. The ponies now often run on better, smaller, grazing areas and they expend less energy getting their food. Most modern animals will also be doing far less work than the stock in early photographs.
Hairiness: classical writers' and sculptors' observations
Xenophon, the Greek cavalry commander whose writings (430-354 BC) are the earliest surviving equestrian record, approves a horse with shaggy "shanks" or lower legs. He describes with approval "crinkly" manes and tails. Xenophon appears to have liked manes left long, rather than hogged or trimmed as was apparently the Greek fashion. Other writers from classical times, such as Sophocles, also describe horses with their manes removed. Xenophon, though, requires a long enough mane to be grasped during mounting.
Roman statues and carvings of horses (see Epona) suggest that manes were either kept hogged or were shortened. Fetlock hair tufts ("foot locks") are in evidence in many carvings and drawings throughout history, though none are as profuse as those of "feathered" modern horses and ponies. Pictish ponies are shown in some carvings with long manes, but they have clean legs.