SUMMARYFive colour characteristics were studied in seventeen carrot trials in which four varieties of the Chantenay type and four of the Autumn King type were grown at two densities at several sites for 3 yr. The Chantenay type had lower percentages of green‐topped and green‐cored roots and a higher score for internal colour; the Autumn King type had a lower percentage of purple‐topped roots. Differences between varieties within types were also detected. Large environmental effects mainly resulted from differences between individual trials. Percentages of discoloured roots were higher at the low density.Genotype × environment (GE) interactions of practical importance were detected for all characters except internal colour. Some of these interactions were adequately described in terms of different linear regression coefficients for the genotypes, when genotypic values were regressed on environmental means. The results indicate that a low density should be chosen when selecting for reduced discolorations. Broad‐sense heritabilities, estimated from variance components for the genotypic, environmental and GE effects, show that the most efficient selection for a colour character, in one season and with four test plots per family, would be achieved when such plots were grown at four separa