The Color of Light & CCT


Color choice is a powerful decision. When you examine the science of color and explore Correlated Color Temperature (CCT) you can better determine how to choose light color for each space. Color can be used to evoke certain moods, boost your work with task lighting and define a space.

Color theory involves a lot of components we could not cover in the length of one blog. Instead, we will examine warm vs. cool light to define those descriptions, explain Correlated Color Temperature (CCT), and also what type of moods you can evoke when you choose cool or warm lights in your unique lighting applications.


The Color of Objects and CRI

As you learned in our blog Understanding the Visible Light Spectrum and Color, sunlight appears as white light to the human eye. Sunco’s equivalent color temperature is 5000K Daylight, which equates to the quality of light seen outside during the middle of a sunny day. Remember that white light is not truly white, it is a combination of all colors in the Visible Spectrum.

The wavelengths of colors – and everything else on the Electromagnetic Spectrum – are either absorbed by objects or reflected/transmitted by them. For instance, a red shirt appears red, because it absorbs every wavelength except red. The red wavelength of light is reflected away from the object and transmitted to your eyes. View a white piece of paper and you see every color of the visible spectrum. A black table absorbs all the colors and reflects none of them.

This complex process is regulated in our eyes by the retina with its two types of photoreceptors: cones and rods. Cones detect color. Rods see black, white, and gray. Cone photoreceptors require light to detect color. You experience this shift when viewing a dark room at dusk. It is hard to distinguish color. You may see things in a gray scale in that scenario, instead of recognizing natural or accurate color.

Color Rendering Index (CRI) indicates the faithful reproduction of an object’s color when under that light source versus when viewed under a natural light source. In this measurement, 100 is shown as the closest to natural or sunlight quality.

When you are searching for lighting with a high CRI (on a scale of 0-100), you want light bulbs that produce accurate color rendering. LED lights in the CRI 80 to CRI 89 range produce accurate color rendering and are considered good. CRI 90+ light bulbs have excellent color rendering ability. Sunco’s LED light bulbs feature a high CRI ranging from CRI 80 to CRI 95. In contrast, fluorescent bulbs produce an unnatural light quality and range in low numbers on the CRI scale.

High CRI also allows the textures of items to stand out as it delivers clear definition. This makes high CRI LED light bulbs ideal for retail, restaurants, patios, dining rooms, and other places where accurate color representation is important.



What is Warm Light vs. Cool Light?

Since you read last week’s blog, you know that red light represents the longest wavelength on the Visible Spectrum, while the shortest wavelength – on the other side of the spectrum – is violet. Let’s define warm and cool colors.

Warm Light – Red, amber, orange, and yellow are the warmer colors of the Visible Spectrum.

Cool Light – Green, blue, violet and purple are the cooler colors.

Sunco’s color temperatures include warmer colors under 3000K (Warm White), which appears yellow. Color tends to shift to cool when you reach 4000K (Cool White). The cool 6000K (Daylight Deluxe) appears silver in nature to our eyes. In our blog on light quality, we show a graphic of the Sunco color temperatures and their appearance, if you want more details on that.

In general, lower color temperatures provide a warmer look and higher color temperatures deliver a cooler look. Now that you understand the definition of warm and cool colors, we can examine the appearance of light, regarding its warmth or coolness.


Understanding Correlated Color Temperature (CCT) When Discussing Light

The word “temperature” in Correlated Color Temperature (CCT) can be a little deceiving, because although we are talking about temperatures when discussing light and CCT, we are not measuring the physical temperature of a light source or light beam. CCT refers to the physical nature of objects and how heating can change the color and appearance of an object.

Solid objects emit radiation when heated to temperatures above absolute zero. That radiation is a form of energy. When you heat a solid object to a high temperature, the light emitted from it does not reflect the composition of that object, but rather is more representative of its temperature.

In the case of a traditional filament light bulb – where a filament inside the glass globe is heated to generate light – the light we see appears within the Visible Spectrum of color.

In physics, scientists use a “black body radiator” as an object to study emission or black-body radiation. To keep things simple, let’s examine color with a black body radiator (an object that absorbs all EM radiation), instead of diving into Planck’s Law 1 and the other laws, theories, and constants involved in the study of this process. After all, we want to see how all that applies to LED light bulbs and CCT, not read a physics lesson.

Understanding this concept begins with a very brief history. Our sun is close to a true black body radiator, but the study of this by the German physicist Gustav Kirchhoff back in 1862 studied a hypothetical or perfect radiator that would absorb all light. He began this work, which was then expanded by Lord Rayleigh, Max Plank, and other scientists in early 20th century.

A great way to understand the concept of a black body radiator is to examine how a blacksmith heats iron at a forge or how industrial factories heat metal into a liquid form to reshape it. The color of metal changes when heated. You have likely seen what this looks like in a variety of how-do-they-do-that videos online. While there is radiation emitted outside of the Visible Spectrum from the process of heating metal, humans only see the visible band of color.

As a side note, chemicals can also change the color of heated metal or other objects.

For our blacksmith example, think about that iron bar held with tongs at the forge:

  • When metal is first heated – still at a relatively low temperature – the metal turns an amber/red hue.
  • Heated metal that is ready to be shaped or worked by a blacksmith is a warm white with a slight tinge of yellow (such as our 3000K color temperature).

In our example of a factory:

  • Liquid metals appear as a bright white or silver (which relates to the daylight quality of 5000K-6500K+). Though the metal itself is piping hot, the actual color of the metal is cool in tone and quality.

When you examine what sunlight looks like throughout the day, you can easily see the effects of color and how it changes. The same applies for other practical examples.


Recognizing Color Temperatures in the World

In our not so distant past, homes were lit with candles or the flames from a fireplace. In contrast to heated metal, the warm tone of candlelight falls at around 2200K. That temperature looks a bit counter intuitive from we expect when we think of temperature ranges. The higher temperatures are not reds, they are blue? Correct. Remember, we are examining how heating can change the color and appearance of an object, not its actual temperature.

You can also look at this in a very simplistic view. Fire is warm/red/amber and water or ice is cool/cold/blue/white. In contrast, when you examine black body radiation and CCT, blue/white is hotter (higher temp) and red/amber hues are cooler (lower temps).

That candlelight color temperature of around 2200K makes a lot more sense now, doesn’t it?

Sunco’s 2200K (Amber Glow) color temperature is considered warm. A warm color and hue in a room can set a certain mood. You wouldn’t want intimate and warm lighting in a space where tasks were performed, like in an office or factory. You would want light that helps energize or invigorate people.

Due to the scattering of light through Earth’s atmosphere. you can easily examine color temperatures in the world around you.

Morning Sun – 2000K to 3000K

Midday (around noon to 1 p.m.) - daylight color temperature range of 5000K to 6000K

Evening Sun – less than 2000K

Switching gears back to color science, remember that the colorful objects in a room can also balance out the lighting color temperature you choose. A room with bright white light can be more welcoming when you toss in warmer colors in your furniture, wall paint, and artwork choices. Contrasting these provides humans with a sense of balance. Also note that cooler colors can help make a smaller room appear to be larger.

Weather can also play a part. If you live in humid regions, you might prefer a cooler color temperature inside, while those in colder regions might desire a warmer color palette in their homes.

Light can create a mood and define room ambiance. Next time you look at advertising photos, examine the type of lighting the photographer used in their image. You can see the warm and cool tones of a room and examine how it makes you feel, what mood it evokes.


How to Create Ambiance with Light

The psychology of color is rather extensive. Here, we will examine only how various color temperatures can create a mood to help you choose the right color temperature.

Humans are affected by lighting and the mood of spaces where we work and live. We respond to this emotionally and also with subdued or energized behavior, depending on the environment.

The effects of light choice are very obvious when applied wrong, such as when someone (not you, of course!) uses a cool brilliant white light in what is intended to be an intimate space. This is also true when someone chose a cozy, warm amber for a large office room filled with cubicles instead of a crisp or invigorating color. Dimming your LED lights can help with this in situations where dual use of a space occurs, when you want to tone down a bright environment to shift the mood as you wind down your day.

If you are also tying in paint palette selections, remember that the neutral side includes warm brown and cool taupe, along with cool white and warm black. 

There are many reasons why you would want to choose warm or cool lighting.

Why Choose a Warm Light? (Red, Amber, Yellow)

Warmer lights are more inviting and calming than cooler tones. They can simulate either early morning or evening light.

Warm light suits general living spaces where people want to comfortably relax. It also sets off decor with wood accents. Cooler light color temperatures also suit evening relaxation at a bar, café or lounge, in addition to the vintage look of LED Filament Bulbs on a patio.


Sunco’s LED high tech smart bulbs offer “scenes” you can select to create a specific ambiance as pre-existing settings or you can create and save your own scenes. Use the choice of color temperature to shift the mood in a dual-purpose space or select a new color from 16+ million colors with our smart bulbs. Tune your color palette or dim the brightness to create more atmosphere.

Both Tungsten (under 2000K) and incandescent lights (around 3000K) fall within the warmer color temperatures, if you are looking to replicate that look when choosing Sunco LED bulbs.

Also recognize that the color of a lamp shade or wall paint can affect our perception of how warm a light appears.

The Circadian Rhythm and regulating a body’s biological clock can be adjusted via lighting. When considering that science, designers may add warmer lights in classrooms to calm students. A choice of a cooler tone is suitable for offices or when you need students to focus.

Why Choose a Cool Light? (White, Blue, Silver)

The cooler side of the spectrum offers a focusing affect with crisp, invigorating, and energizing light to appeal to the human intellect. The cooler color temperatures are ideal for task lighting in kitchens, offices, and commercial spaces.

When you shift to the 6000K range and above, this is what you need for security lights, retail or display (with a high CRI for accurate color rendition), laundry rooms, and warehouses.



Fluorescent tubes (3000K to 6500K) fall within the cool range of the color spectrum. Sunco offers LED Tubes as replacement bulbs for your existing tube light fixtures as low wattage alternatives to traditional bulbs. We also offer LED Shop Lights (flush mounted, wraparound, and suspended chain fixtures) and Integrated T5 fixtures. You can choose which color temperatures best suits your specific lighting application.


Emotions, mood, and the ambiance you create with lights all play a part on how we perceive the spaces where we work and dwell. Understanding the way color temperatures, and the selection of cool vs. warm light, affect the people who will use a space can help you create an ideal lighting plan for your unique situation.

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