This document is a reference document to support the correct measurement of the colour of finished leather by instrumental means. The document describes general concepts of colour measurement adapted to leather and the calculation of differences in colour. This document defines the following: a) the use of D65 as the standard light source for the leather industry; b) the use of D65 light source 10º as standard conditions for colour matching, for the definition of daylight simulators, and as the reference light source for metamerics analysis; c) the use of CIE DE2000 as the colour difference formula.