With over 130 colours to identify, many of which are quite similar, the make of the sanitaryware eliminates most of the possible mismatches as each manufacturer produces a limited number of colours
If the official sanitaryware colour is not known, the make, age, and a general description of the colour should allow us to narrow down the colour and send some samples for confirmation
A digital photo of the basin and toilet is always useful as although the exact colour reproduction is not reliable, we can identify the make and an indication of the colour enough to send a few samples for final confirmation.