Colour measurements were analyzed by considering the CIELAB colour system (CIE, 1986), which represents each colour by means of three scalar parameters or the Cartesian coordinates: L*, lightness or luminosity of colour, which varies from 0 (absolute black) to 100 (absolute white); a*, associated with changes in rednesse greenness (positive a* is red and negative a* is green); and b*, associated with changes in yellownesseblueness (positive b* is yellow and negative b* is blue). Alternatively, each colour is represented by means of three angular parameters or cylindrical coordinates, most closely related to the psychophysical perception of the colour: L*, lightness or luminosity of colour, also defined in both scalar and angular colour sets; chroma or saturation ðCab* ¼ ða*2 þ b*2Þ1=2Þ related to the intensity of colour and hue angle (hab ¼ arctan (b*/a*)) or tone of colour which refers to the dominant wavelength and indicates redness, yellowness, greenness, or blueness on a circular scale, starting at 0 and increasing counterclockwise (Wyszecki and Stiles, 1982).