Colour has been a key element within the design of tweeds from the 1830s up until today. This chapter focuses on interdisciplinary and material culture research about nineteenth-century tweed design, which shows that novel ways of using colour evolved from the 1830s in Scotland. It investigates for the first time how the significant focus on colour, design and fashionable novelty in Scottish mill-based tweed manufacturing interconnected with important technological changes in dye chemistry between 1858 and 1914. This essay is broadly situated within the significantly under-researched fields of wool textiles and design, and textiles and masculinities between 1829 and 1914. It extends the existing literature on artificial dyes, colour and fashion between 1856 and 1914, which has almost exclusively focused on textiles designed for womenswear. The influence of the ideas of the psychologist J.C. Flugel and John Harvey’s Men in Black has tended to persist within the literature on colour, fashion and synthetic dyeing in the late nineteenth and early twentieth centuries. By contrast, this study investigates the nuanced use of colour within the Scottish tweeds that were increasingly worn by men within the modern contexts of informal daywear, sport and leisure between 1829 and 1914. It further challenges the lingering acceptance of the Flugellian idea that nineteenth century textiles for menswear exclusively came in ‘austere’ black, or dark colours that were expressive of singular masculine ideals of middle class sobriety and asceticism.