“A Delta E 2000 value of 1 is the threshold below which a colour difference is imperceptible.”

1 Delta E 2000 as the perceptibility threshold is stated verbatim by Source 1 (Techkon/Datacolor), a vendor blog, but Source 2 contradicts the figure: the peer-reviewed 2024 J Clin Exp Dent study measured 50%:50% perceptibility thresholds of Delta E 2000 = 2.29 for dentists and Delta E 2000 = 2.27 for patients — over twice the claimed value. Source 2 is the better authority, being a controlled visual study under D65 illumination with stated statistics, whereas Source 1 offers the '1' figure as a generalization with no supporting data; the claim is therefore only defensible as a rule of thumb, not as a measured threshold.