Usually Red light is used as a night vision. The red light will not cause your pupil contraction, and lighting extinguished, your eyes do not need to re adapt to the dark. Red is usually in monochrome print processing is used as a “safe” color, because it will not damage of printing negatives。 yellow light has some advantages of red light and white light. Yellow light another advantage is that when you are reading less，because of long time reading cause eye fatigue Under blinding and reflection light。Green light can also be used as a night vision; the green light is especially suitable for reading a map or chart during the night. It is not so easy to be found by night vision equipment, are vulnerable to human discovery, bright green light lower than red.Blue light can be used to map reading; it is often favored by military personnel in the night, because blue light increased the contrast level. It can also be used as background work lights theatre and the performances of the color ighting.Blue&green light have similar advantages with green light at night vision, but with the color characteristics of blue-green light increases, some users like blue&green light for this reason.Red is used together with infrared night vision equipment. Otherwise, the human eye is invisible to infrared led light.Ultraviolet light is usually used as identification whether the banknote forgery, some UV light emitting diode lighting is popular in nightclubs and parties, they are used to make fluorescent material emits more light.The color of the light and light wavelength whether we can see The color of the light is determined by its wavelength, the units of light wavelength is nano ，also said to be 1/1000000000 meters. The following is the color of the light wavelength.
In the infrared glow
4600nm – 1600nm – no visible light
Low infrared light
1300nm – 870nm – no visible light
850nm – 810nm – hardly visible light
Near infrared light
780nm – when the direct observation can be seen a very dark cherry red light
770nm – when the direct observation can see a deep cherry red light
740nm – deep cherry red light
The red light
700nm – deep red
660nm – red
645nm – a bright red
630nm – Orange red
620nm – Orange
The orange light
615nm – orange light
610nm – the orange light
605nm – amber light
The yellow light
590nm – “sodium” yellow
585nm – yellow
575nm – lemon yellow / light green
The green light
570nm – light greenish blue green
565nm – Green
555nm – 550nm – fresh green
525nm pure green
505nm – Green / blue green
500nm – light green blue
495nm – sky blue
Blue
475nm – azure blue
470nm – 460nm- bright blue
450nm – pure blue
Blue purple
444nm – dark blue
430nm – blue and purple
Violet light
405nm – pure purple
400nm – Deep Purple
Near ultraviolet light
395nm – reddish purple
UV-A type ultraviolet light 370nm is almost not visible, by wood glass filter is displayed at a dark purple.White light emitting diodes have to purplish white yellowish. White light emitting diode temperature range as low as 4000°K to 12000°K. Common white light emitting diode as 6500°- 8000 K.