Worn items are a crucial part of non-verbal social interaction that simultaneously exhibits communal, cultural, and political structures and individual preferences. This thesis examines the role of fictional costume and colour in constructing identities within two fourteenth-century Arthurian verse narratives: Froissart’s Middle French Meliador and the anonymous Middle English Sir Gawain and the Green Knight. To emphasise the imaginative value of material cultures and discuss the potential reception of fictional objects, the argument draws on illuminations from nine manuscripts of prose Arthurian stories. Particularly stressing the role of colour in garments, the first chapter examines the issues of analysing literary costume, reviews the provenances of the texts and illuminations, and establishes the relevant historical background concerning fashion, symbolism, and materials of construction (such as fabric, dyes, and decorations). This is followed by two chapters on men’s items. First, the use of courtly clothes and colour-related epithets in manipulating perception and deceiving internal and external audiences is explored. Second, the symbolic value of arms and armour in tournament society is evaluated alongside the tensions between war and armed games that such tools reveal. Chapter four expands on the preceding chapters by discussing the application of heraldry as a malleable identifier. Chapter five considers how ladies’ garments, bodies, and character are coalesced and separated through adoption or rejection of literary techniques, thereby creating conflict between noblewomen as social commodities and as persons with narrative agency. The final chapter analyses the employment of wearable items as gifts and commodities and how such objects can alter interpersonal relationships. Colour and costume are a means by which narratives can explore, accept, or reject literary topoi. Their myriad functions allow the active manipulation of identity, relationships, and internal and external audiences. By focusing on the pluralities and ambiguities of meaning connected to colour and costume, this thesis explores how these materials mediate between conflicting connotations to create new meanings within the narratives.