Table 1. Pearson Correlation coefficients (r) between pairs of eye colour phenotype measures obtained with various methods in the European study population (N = 3,087), lower triangular matrix depicts corresponding P-values.

Eye colour measure	Nonpigmentation#	Pheomelanin#	Eumelanin#	Hue	Saturation	Colour score	L	a*	b*	PIE score	T-index
Nonpigmentation#	1	−0.64	−0.58	0.62	−0.74	0.57	−0.68	−0.66	0.93	−0.71	−0.61
Pheomelanin#	<1e–300	1	−0.06	−0.11	0.60	0.14	0.34	0.76	−0.68	0.29	0.13
Eumelanin#	1.12E–273	1.19E–03	1	−0.51	0.69	−0.52	0.71	0.38	−0.60	0.67	0.73
Hue	<1e–300	3.05E–09	1.10E–206	1	−0.37	0.73	−0.74	−0.07	0.51	−0.52	−0.86
Saturation	<1e–300	1.07E–299	<1e–300	2.57E–100	1	−0.17	0.81	0.89	−0.83	0.66	0.72
Colour score	1.12E–268	3.64E–14	1.43E–213	<1e–300	1.38E–21	1	−0.43	0.07	0.42	−0.47	0.71
L	<1e–300	1.38E–86	<1e–300	<1e–300	<1e–300	1.68E–139	1	0.53	−0.68	0.67	−0.76
a*	<1E–300	<1e–300	2.35E–104	3.65E–05	<1e–300	4.24E–05	8.11E–226	1	−0.74	0.50	0.97
b*	<1e–300	<1e–300	5.38E–303	4.20E–206	<1e–300	1.25E–130	<1e–300	<1e–300	1	−0.67	0.36
PIE score	<1e–300	6.12E–63	<1e–300	2.78E–217	<1e–300	1.16E–172	<1e–300	9.69E–197	<1e–300	1	−0.55
T-index	1.13E–300	1.18E–12	<1e–300	<1e–300	<1e–300	<1e–300	<1e–300	<1e–300	3.71E–92	5.99E–241	1

^#Estimated with the new computational approach introduced here, for the methods used to measure the other eye colour scores, see text.