Background Front-of-pack (FOP) nutrition labels are considered helpful tools to help consumers making healthier food choices, thus improving their diet. In France, the implementation of a FOP nutrition label-the 5-Colour Nutrition Label (5-CNL)-is currently under consideration. Our objective was to investigate dietary profiles in a French adult population using the 5-CNL, and to assess its potential impact in improving the diet through substitution of foods. Methods and Findings Subjects included in the NutriNet-Sante cohort, who had completed three 24-h dietary records were included in this cross-sectional analysis. Mutually exclusive clusters of individuals were identified using the percentage of energy derived from foods of each of the 5-CNL colours as input variables. Three scenarios of substitution of foods for healthier alternative using the 5-CNL were tested. Food group and dietary intakes, socio-demographic and lifestyle data were compared across clusters using ANOVAs or Chi-square tests, as appropriate. We identified three mutually exclusive dietary profiles: 'Healthy' (N = 28 095, 29.3% of the sample), with high consumption of fruit, vegetables, whole cereals and fish; 'Western' (N = 33 386, 34.8%); with high consumption of sweetened beverages, breakfast cereal, cheese, fatty and sugary foods; 'Traditional' (N = 34 461, 35.1%), with high consumption of potatoes, bread, meat and dairy desserts. Overall, substitutions strategies led to an increase in the number of subjects reaching the recommended intakes in energy, macro and micronutrients. Increases were particularly high in the 'Western' pattern for lipids and saturates intakes: from 16.2% reaching the recommended amount for lipids (13.5% for saturates) to 60.6% and 85.7% respectively. Conclusion The use of the 5-CNL as an indicator of food choice meaningfully characterizes clusters of dietary habits and appears as an effective tool to help improving the nutritional quality of the diet.