Table 3 Colour variation measurements in CIELAB 1976 colour space induced by accelerated ageing

 − 0.41

 − 8.23

 − 0.13

1.90

 − 0.48

12.10

1.13

14.76

 − 0.90

 − 3.44

0.07

0.40

1.73

1.05

1.99

3.66

 − 0.04

 − 2.30

 − 0.40

0.38

1.54

3.38

1.68

4.16

1.50

 − 3.30

 − 0.04

0.64

 − 0.11

2.66

1.80

4.32

 − 0.24

 − 3.43

 − 0.03

0.45

0.49

4.39

0.87

5.61

 − 0.46

 − 3.33

 − 0.02

0.78

1.22

5.06

1.40

6.13

0.54

 − 4.63

 − 0.01

0.56

0.49

3.01

0.85

5.56