2.3.4. Measurement of color
CIE (Internationale de l'éclairage) scale was considered to quantify
the color of the sample in a three dimensional domain where L*
(lightness), a* (red to green) and b* (yellow to blue) are the corresponding
mutually perpendicular axes. A portable colorimeter
(model: Spectro-guide 45/0 gloss; make: BYK Gardner, Geretsried,
Germany) was used to estimate the color parameters after calibrating
against three standard tiles viz. green, black and white. The total color
change (ΔE*) was calculated according to Eq. (2).