In order to measure the difference between two colors, the difference is assigned to a distance within the color space. In an equidistant-method color space, the color difference ∆E can be determined from the distance between the color places:
ΔE = √ (L*₁-L*₂)² + (a*₁-a*₂)² + (b*₁-b*₂)².
0: No color difference
1: Slight color difference
2: Small color difference
3: Medium color difference
4: Large color difference
5: Very large color difference
In industrial color measurement, color differences between 0 and 1 often play an important role.