**Abstract**

This book chapter covers principles and few case studies on colorimetric Estimation of (i) determining purity/active ingredient % of selective dyes/pigments (ii) Identification of any colorants to distinguish from other similar compound, (iii) Measurement of surface colour strength of a dyed textile, (iv) Measurement of colour differences by estimating DE, DL\*, Da\*, Db\*, DC and DH values, (v)- Computer-aided colour match prediction for any standard shades, (vi) Estimation of compatibility of two dyes/colourants to use for compound shades, (vii) Determination of rate of dyeing, dyeing isotherm and dyeing kinetics to control dyeing, (viii) Optimization of dyeing process variables, (ix) Precession grading of Colour Fastness of dyed textiles on fading under different ways/agencies and (x) Estimation of Soil Removal efficacy of different detergent used for textiles. These colorimetric measurements are found to be very useful for effective process and product control of dyed textile materials. Selected Case studies on all the above colorimetric applications with specific example or experimented data are discussed for each of the method under reference. Finally, the other applications of colorimetric analysis besides textiles industry are also mentioned in concluding remarks.

**Keywords:** colour quantification, CIE-L\* a\* b\* colour space, colour matching of textiles, standardization of dyeing process variables, colour fastness grading, UV VIS absorbance spectrophotometer, UV VIS reflectance spectrophotometer, soil removal efficacy of detergent
