The tristimuli coordinates,
lightness (L*),
redness (a*)
and yellowness (b*),
were recorded,
and the hue angle (H*)
and chroma (C*)
indexes were calculated as H*= tan−1(a*/b*)×57.29,
expressed in degrees,
and C∗ = a∗2 + b∗2.
The absolute value of the integral of the translated spectrum (SUM) was calculated according to Prache and Thériez (1999).
Briefly,
the reflectance spectrum was collected every 10 nm between 450 and 510 nm, and it was then translated (TR) to make the reflectance value at 510 nm equal to zero.
On the translated spectrum, the integral value (SUM) was calculated as follows: