Have you ever wondered what light really is? In this post, we’ll explain what light is all about, and break down light wavelengths, light colors, and which wavelengths of light are used for light therapy.
What is Light?
Light comes to the earth from the sun, in the form of electromagnetic waves that carry energy. Humans are able to see the world around us because wavelengths of light shine on the earth and reflect back to our eyes. But not all waves of light are visible. And only a few select wavelengths of light are suitable for light therapy treatments. [1,2,3]
What are wavelengths of light?
Waves of light are made of electricity and magnetism, which is why we call them electromagnetic waves.  Waves of light travel extremely fast through space and time, but all light is not the same. We measure light by wavelength, or the distance between each wave. The electromagnetic spectrum contains all the light that exists, organized in order of wavelength.
The electromagnetic spectrum is very wide. At one end are low-energy gamma rays and X-rays that have the longest wavelengths. On the other end of the spectrum are high-energy radio and micro waves that have the shortest wavelengths. In between, on a tiny sliver of the spectrum, we see visible light in all its colors and glory. 
When we think about light, we usually think about visible light. Humans can only detect light with waves from 400 nanometers to about 700 nanometers. We see these waves as the colors of the rainbow. We can see the world around us because waves of visible light shine on objects, and reflect back to our eyes. [5,6,7,8]
Colors and Wavelengths of Visible Light
The visible light portion of the electromagnetic spectrum is separated into different wavelengths and colors of light.
Violet light (380-450 nm) has the shortest waves on the visible spectrum. Violet light is not used for light therapy because these wavelengths haven’t been shown to produce health benefits when they’re isolated. [5,6,7,8]
Blue light (450-495 nm) is best known for being isolated to produce the bright light of computer, television, and cell phone screens. Blue light is good at making things bright, which is why it’s used in so many electronics. Blue light is also isolated and used in light therapy treatments for facial skin and acne. [5,6,7,8]
Green light (495-570 nm) is only recently being studied for therapeutic effects. Some early studies have shown positive results for reducing inflammation and migraines, but green light has not been widely used in light therapy yet.
Yellow light (570-590 nm) and Orange light (590-620 nm) are still being studied, and haven’t been isolated for use in light therapy devices yet. [5,6,7,8]
Red light in the 620-750 nm range is the color of light most often used for light therapy treatments. Red and near infrared (NIR) light has been widely studied and tested in peer-reviewed clinical trials and studies, with overwhelmingly positive results for skin and general health, with few side effects or risks. [9,10]Some people in the wellness world talk about the colors of chakras, but this is not based in physics like the electromagnetic spectrum.
Light is Important for Good Health
So why is light important for human health? All life on earth relies on the sun and its energy, and people are no exception. Light is our primary source of energy, and our cells need photons of light to produce adenosine triphosphate (ATP), or cellular energy. Specific wavelengths of light have also been shown to have therapeutic effects for people, from reducing pain and inflammation, to improving skin and muscle recovery. [9,10,11] That’s where light therapy comes in.
Sunshine is full-spectrum light, meaning rays of sunshine contain all wavelengths of light, both visible and invisible. Different wavelengths and colors have different physiological effects on people’s health and wellness. Some wavelengths of light can be harmful, like taking in too much UV radiation from the sun. Other wavelengths and colors of light, like red and near infrared (NIR) light, can have specific positive effects on human cells and health.
Light Therapy Colors and Benefits
While some devices advertise full-spectrum light, color light therapy is the standard for effective light treatments. Red light wavelengths are most commonly used for light therapy because they’ve been studied the most and shown to produce positive results for people. [9,10] Isolating wavelengths of light in the 620 to 750 nanometer range has shown positive results for everything from skin health to muscle health.
This is why phototherapy devices like Luminance RED isolate red light wavelengths to address cold sores, canker sores, and other skin conditions.
Light therapy colors like orange, yellow, and green light do not seem to produce similar benefits for people when they’re isolated and used in clinical settings. Blue light may have some benefits for certain skin issues, but blue light also comes with greater risks for eyes and headaches.
Conclusion: Red Light Wavelengths are Best for Color Light Therapy
Light powers everything we do on earth. Different wavelengths and colors of light come from the sun and have different effects on people when they’re isolated and used for medical or cosmetic treatments. Red light wavelengths in the 620 to 750 nm range have shown the best results for color light therapy to date. That’s why red light therapy has become so popular, while other colors of light like green and yellow aren’t widely used for light therapy.
Sources and References:
 CIE (1987). International Lighting Vocabulary. ISBN 978-3-900734-07-7.
 Pal, G.K.; Pal, Pravati (2001). Textbook of Practical Physiology(1st ed.). Chennai: Orient Blackswan. p. 387. ISBN 978-81-250-2021-9.
 Buser, Pierre A.; Imbert, Michel (1992). Vision. MIT Press. p. 50. ISBN 978-0-262-02336-8.
 University of Wisconsin Physics. What is Light?
 Lynch, David K.; Livingston, William Charles (2001). Color and Light in Nature(2nd ed.). Cambridge: Cambridge University Press. p. 231. ISBN 978-0-521-77504-5.
 Elert, Glenn. “The Electromagnetic Spectrum, The Physics Hypertextbook.” Hypertextbook.com.
 Kumar, Narinder. 2008. Comprehensive Physics XII. Laxmi Publications.
 Laufer, Gabriel. 1996. Introduction to Optics and Lasers in Engineering.
 Avci P, Gupta A, Sadasivam M, Vecchio D, Pam Z, Pam N, Hamblin MR. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Semin Cutan Med Surg. 2013 Mar.
 Hamblin M. “Mechanisms and applications of the anti-inflammatory effects of photobiomodulation.” AIMS Biophys. 2017.
 Cleber Ferraresi, Ying-Ying Huang, Michael R Hamblin. Photobiomodulation in human muscle tissue: an advantage in sports performance? J Biophotonics. 2016 Dec;9(11-12):1273-1299