A method for determining the colour fidelity (ΔE) and/or for ascertaining the perceivable colour difference (ΔE) for humans between two colours predetermined by colour vectors (E 1, E 2), - the two colour vectors (E 1, E 2) being defined with respect to a predetermined colour space, - each of the components of the respective colour vector (E 1, E 2) corresponding in each case to the brightness measurement value of a sensor (10, 11) for a predetermined wavelength or a predetermined wavelength range, characterised in that, - the colour deviation (ΔR) is ascertained in the colour space between the two colour vectors (E 1, E 2), - a base colour vector is defined by one of the two colour vectors (E 1, E 2) or by linking the two colour vectors (E 1, E 2) in the colour space, - in that a multiplier (ΔÊ) is ascertained by selection from a number of predetermined multipliers (ΔÊ 1,..., ΔÊ n) as a function of the base colour vector, in that - a quantisation space comprising a number of vectors (q) is predetermined, - an assignment for each colour vector (e) within the colour space to one of the vectors (q) in the quantisation space is predetermined, all the colour vectors (e) of the quantisation space mapped onto the same vector (q) each being within a predetermined environment (u), and the assignment mapping adjacent environments (u) of colour vectors (e) onto respective adjacent vectors (q) in the quantisation space, - each vector (q) within the quantisation space is respectively assigned a multiplier value (ΔÊ(q)), - for the base colour vector, the vector (q) assigned thereto in each case by the assignment is searched for and assigned thereto as the quantisation vector, and - the multiplier value (ΔÊ) assigned to the respective quantisation vector is ascertained and used as a multiplier (ΔÊ), - the selected multiplier (ΔÊ) approximating the ratio of the distance (ΔE local) of colour vectors transformed into the CIELAB colour space to the distance of these colour vectors in the predetermined colour space within a predetermined environment around the base colour vector, and - in that the perceivable colour difference (ΔE) or the colour fidelity (ΔE) is ascertained as the product of the colour deviation (ΔR) and the multiplier (ΔÊ) according to ΔE = ΔR · ΔÊ. - the two colour vectors (E 1, E 2) being defined with respect to a predetermined colour space, - each of the components of the respective colour vector (E 1, E 2) corresponding in each case to the brightness measurement value of a sensor (10, 11) for a predetermined wavelength or a predetermined wavelength range, characterised in that, - the colour deviation (ΔR) is ascertained in the colour space between the two colour vectors (E 1, E 2), - a base colour vector is defined by one of the two colour vectors (E 1, E 2) or by linking the two colour vectors (E 1, E 2) in the colour space, - in that a multiplier (ΔÊ) is ascertained by selection from a number of predetermined multipliers (ΔÊ 1,..., ΔÊ n) as a function of the base colour vector, in that - a quantisation space comprising a number of vectors (q) is predetermined, - an assignment for each colour vector (e) within the colour space to one of the vectors (q) in the quantisation space is predetermined, all the colour vectors (e) of the quantisation space mapped onto the same vector (q) each being within a predetermined environment (u), and the assignment mapping adjacent environments (u) of colour vectors (e) onto respective adjacent vectors (q) in the quantisation space, - each vector (q) within the quantisation space is respectively assigned a multiplier value (ΔÊ(q)), - for the base colour vector, the vector (q) assigned thereto in each case by the assignment is searched for and assigned thereto as the quantisation vector, and - the multiplier value (ΔÊ) assigned to the respective quantisation vector is ascertained and used as a multiplier (ΔÊ), - a quantisation space comprising a number of vectors (q) is predetermined, - an assignment for each colour vector (e) within the colour space to one of the vectors (q) in the quantisation space is predetermined, all the colour vectors (e) of the quantisation space mapped onto the same vector (q) each being within a predetermined environment (u), and the assignment mapping adjacent environments (u) of colour vectors (e) onto respective adjacent vectors (q) in the quantisation space, - each vector (q) within the quantisation space is respectively assigned a multiplier value (ΔÊ(q)), - for the base colour vector, the vector (q) assigned thereto in each case by the assignment is searched for and assigned thereto as the quantisation vector, and - the multiplier value (ΔÊ) assigned to the respective quantisation vector is ascertained and used as a multiplier (ΔÊ), - the selected multiplier (ΔÊ) approximating the ratio of the distance (ΔE local) of colour vectors transformed into the CIELAB colour space to the distance of these colour vectors in the predetermined colour space within a predetermined environment around the base colour vector, and - in that the perceivable colour difference (ΔE) or the colour fidelity (ΔE) is ascertained as the product of the colour deviation (ΔR) and the multiplier (ΔÊ) according to ΔE = ΔR · ΔÊ.