Above is a picture taken from tree, which leafs are turned from green to orange. The spectrum measured from a orange leaf can be seen below.

Color coordinates calculated from the spectrum
Spectrum Orange
x 0.4975
y 0.3871
z 0.1154
X 20.9232
Y 16.2788
Z 4.8540
R 32.6094
G 12.8694
B 4.7730
L* 47.3382
a* 29.0064
b* 38.2503
u' 0.2993
v' 0.5239
u* 62.5100
v* 34.0809

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