Synthetic dyes that are released to the environment from textile dyeing are harming the health of humans and other organisms. Dye-free coloured cotton provides an alternative to the use of toxic synthetic dyes. However, naturally coloured cotton has low yield, poor fibre quality and a limited range of colours. Generating coloured cotton is a scientific and industrial challenge to achieve high productivity, quality, and more colour-options for a more ecofriendly industry. Here we present a novel example of pink fibres generated in the world’s largest plant-fibre crop, through the expression of the betalain pigment pathway in Gossypium (Malvaceae) cotton fibres. Betalain pathway genes, namely BvDODA1 (red beet, Beta vulgaris), BvCYP76AD1 (red beet, Beta vulgaris) and MjcDOPA5GT (four o'clock flower, Mirabilis jalapa) were expressed under a constitutive promoter (2 × 35S), or a mid-late stage LTP cotton fibre-specific promoter, respectively. The pigment is strongly expressed, retained late in development with the fibre-specific promoter (Li et al., 2023; Pettolino et al., 2023, patent WO/2023/225710). The pink fibres have the potential to reach similar quality to control fibres. This proof of concept in-planta for cotton demonstrates the significant potential of genetic engineering and synthetic biology to generate high quality cotton fibres with more diverse colours for a more sustainable textile industry.