Under the research study, the meat colour was determined of Pekin ducks raised for 11 weeks; the determination was made with regard to the sex and carcass weights grouped in four value ranges. The ranges of carcass weights: (i) PI from 1567 to 2170 g; (ii) PII from 2171 to 2330 g; (iii) PIII from 2331 to 2510 g; and (iv) PIV from 2511 to 2949 g were set so as to obtain the same number of samples in the individual groups. The colour of breast and leg muscles was measured instrumentally using a colorimeter, according to a CIE L*a*b* system. The hue (h) and the saturation (C) of colour were also determined. It was found that the sex of ducks had no effect on any of the colour components of breast or leg muscles. It was proved that the carcass weight affected only the development of the yellow colour (b*) and the hue (h) of leg muscles. The fat content in the muscles depended on the carcass weight and the sex of the birds. A correlation was proved to exist between that trait and the brightness of breast muscle (r = 0.581) and leg muscles (r = 0.763). Only in the case of female ducks, a significant difference (p ≤ 0.05) was confirmed to exist between the lightness (L *) of breast muscles from the groups with lighter carcasses (PI and PII) and the breast muscles from the group of the heaviest carcasses (PIV). A significant difference (p ≤ 0.05) was found in the fat content in the muscles from the same groups. It was confirmed that in order to get the meat (to be used as a raw material for further meat processing) of even colour, male and female Pekin ducks should be raised separately. Moreover, the female ducks should not be raised longer than until their carcass weight reaches 2500 g, i.e. until those birds reach a body weight of 3500 g.