Colorimetric conformance shall be verified by printing each ink on the reference substrate, described in Annex A, at a range of ink film thicknesses. The colours of the resultant test prints shall be measured and the colour difference determined between the sample and the pertinent value given in Table 1. If at least one of these samples has a smaller colour difference than that specified in 5.2, the ink conforms colorimetrically to this part of ISO 2846.