The reflectance instruments determined three colour
parameters: lightness (L⁄), redness (a⁄), and yellowness (b⁄).
Numerical values of L⁄, a⁄ and b⁄ were converted into DE⁄ (total
colour difference), DC (chroma) and hue angle (h) according to
Eqs. (2)–(4), respectively. colour measurements were taken in
quintuplicate.