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Usually, we think of an apple as being red.
This is not the same red as that of a cherry or tomato.
A lemon is yellow and an orange like that of its name.
Bricks vary from beige to yellow to orange,
and from ochre to brown to deep violet.
Foliage appears in innumerable shades of green.
In all these cases the colors named are surface colors.
In a very different was, distant mountains appear uniformly blue,
no matter whether covered
with green trees or consisting of earth and rocks.
The sun is glaring white in daytime, but it is full red at sunset.
The white ceiling of houses surrounded by lawns or the white-painted
eaves of a roof on a sunny day appear in bright green, which is
reflected from the grass on the ground.
All these cases present film colors.
They appear as a thin, transparent, translucent layer between the eye and an object, independent of the object's surface color.
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