Colour plays an important role among the quality traits of durum wheat, attracting consumer attention for the pasta market. The traits involved in colour expression are affected by genotype, environment, and processing. In the present study, based on eighteen durum wheat genotypes grown in eight environments, the effects of different traits related to colour expression were evaluated. Carotenoid pigments, such as lutein and β-carotene content; yellow and brown indices; and lipoxygenase, peroxidase, and polyphenoloxidase activities were analysed in semolina. The effects of processing were evaluated by measuring both the content of carotenoid pigments and colorimetric indices in pasta. The genotype, the environment, and their interaction were significant for all traits, although with a strong prevalence of genotypic effects, except for the brown index. After processing, a decrease in carotenoid content and the yellow index (86.7% and 16.0%, respectively) was observed, while the brown index increased (8.2%). A multiple regression analysis was performed on semolina traits, and the yellow index emerged as the main predictor for pasta colour, strengthening this trait as a fast and reliable criterion of selection. A High-Performance Index tool was also used to identify the genotype and environment that better combine all traits, positively influencing colour expression. All this information can be used in durum wheat breeding programmes for the prediction of pasta colour.