Conversely, the colour of prawns increased rapidly in response to white substrates, all within 15 min with the exception of the 0 mg/kg treatment which was not measured at that time (Table 3). However RGB values of animals fed either 50 or 100 mg/kg Axn did not increase as much as those that had been fed 0 or 25 mg/kg Axn. G and B values for the 50 and 100 mg/kg Axn treatments were significantly lower than the G and B values of the 0 and 25 mg/kg Axn treatments, indicating the presence of more blue and green pigments. Indeed, the 100 mg/kg Axn fed animals exposed to white substrates for 2 h showed no significant increase in the R or B values prior to exposure. After exposure to white substrates, results indicated that animals on low carotenoid diets became significantly lighter than those on high carotenoid diets.