Allah says in the holly Quran :
(So I do call to witness what ye see* And what ye see not) (SURAH AL HAKAH:54)
Human vision is limited. As there are many things we can’t see with our eyes even though they exist. That is our vision is restricted to a given range of colours between the red and violet colours. since we are unable to see the ultraviolet and infrared colours.
The wave length of colours:
Violet 750 nanometres
Blue 634 nanometres
Green 570 nanometres
Yellow 520 nanometres
Orange 500 nanometres
Red 434 nanometres
Infrared 300 nanometres
Therefore some colours are visible and others are not
The retina of the eye contains 10 layers, the last one of which is composed of 140 millions of light receptors from rods and cones. A nerve emerges from the eye to the nervous system accommodating 5000 neurons.
It is a miracle that if the green colour is degraded to 8000 grades the eye would be able to differentiate between two of them.