The club initially played in Harrovian blue, latterly with a union flag on the left breast.
The original club crest was a crossed pair of rivet hammers; tools commonly used in the iron and shipbuilding industry. A castle was later (circa 1903/04) added to the crest and represents a prominent local building, Green Street House, which was known as "Boleyn Castle" through an association with Anne Boleyn. The manor was reportedly one of the sites at which Henry VIII courted his second queen, though in truth there is no factual evidence other than the tradition of rumour.
The castle may have also been added as a result of the contribution made to the club by players of Old Castle Swifts, or even the adoption (in 1904) of Boleyn Castle FC as their reserve side when they took over their grounds on the site.
Adidas took over as West Ham's kit supplier for their first season back in the top division in 1980 and their new strips featured a redesigned crest. This was dropped in 1983 in favour of a simple crossed hammer design but it was reinstated in 1985. After 1987 the colours were changed from gold on blue to light blue on claret.
The crest was redesigned and updated by London design agency Springett Associates in the late 1990s, featuring a wider yellow castle with fewer cruciform "windows" along with the peaked roofs being removed; the tops of the towers had previously made the castle appear more akin to Disneyland's Sleeping Beauty's Castle than a functioning fortress. The designer also altered other details to give a more substantial feel to the iconography.
When the club redesigned the facade of the stadium (construction finished 2001/02) the 'castle' from the later badge was incorporated into the structure at the main entrance to the ground. A pair of towers are now prominent features of the ground's appearance, both bearing the club's modern insignia (which is also located in the foyer and other strategic locations).