This proposal outlines a cutting-edge five year project which will push the frontiers of colour category research, and will resonate throughout the cognitive and social sciences. Humans can discriminate millions of colours (Zeki, 1993), yet language refers to colour using a number of discrete categories (e.g., red, green, blue). These colour categories are also present in ‘thought’ (e.g., in colour judgements / memory). There has been considerable multidisciplinary research into the origin of colour categories and how colour categories in thought and language relate. However, major theoretical challenges remain. The ‘CATEGORIES’ project, led by Franklin, will tackle these crucial challenges with the aim of establishing a new theoretical framework for the field. So far, Franklin has made a major contribution to the field by providing converging evidence that infants categorise colour. The ‘CATEGORIES’ project will investigate new ground-breaking questions on the relationship of these ‘pre-linguistic’ colour categories to the world’s colour lexicons, using a diverse range of methods (e.g., infant testing, computational simulations, psychophysics). The project also aims to resolve the long standing debate about the impact of colour terms on perception (e.g., Whorf, 1956), pioneering a ‘Neuro-Whorfian’ approach to the debate. This approach will use neuro-physiological methods to firmly establish the extent to which speakers of different languages ‘see’ colour differently. The new questions, approaches, data and theory provided by the ‘CATEGORIES’ project, will lead to major advances in colour category research. The project will also lead to major advances on issues that are fundamental to understanding the complexity of the human mind (e.g., the interaction of language and thought; how the brain categorises the visual world), having impact across multiple disciplines (e.g., cognitive neuroscience, linguistics, psychology), as well as practical application.