What is the temperature of blue? Is blue warm or cool? When I started studying color over 20 years ago, I distinctly remember the conversations around color temperature. I found them a tad confusing.
We know the common categories or hues of colors and we know which are ‘cool’ and which are ‘warm.’ I like to call this the ‘”Big Picture of Color Temperature.” Hence, when we look at a color wheel, like the one below, we agree that the ‘cool’ colors are: green, blue and purple, and that the ‘warm’ colors are: yellow, orange, and red.
In the painting world, we break it down to another level or subset of ‘cools’ and ‘warms,’ by referring to each primary paint color as being one or the other.
For example, a green-yellow is a ‘cool’ yellow and a orange-yellow is a ‘warm’ yellow. For red, a blue-red is the ‘cool’ variation and a orange-red is the ‘warm.’ Identifying the ‘warm’ and ‘cool’ of yellow and red was fairly easy.
Then along comes blue and the world is not in agreement. There is no consensus as to which blue warm or cool. The most important concept to learn and understand is to SEE the color bias of the blue and not to get all tangled up on temperature – it really can get messy trying to determine if blue is warm or cool.
The best way to SEE the color bias of your blues, is to create a chart like the one below. (For directions on how to create a Pigment Chart, visit my blog post by clicking here.)When you look at this chart of blues you can see which ones carry a red bias and which have a yellow bias. (Color bias refers to that other color nearly every primary tube of paint carries. Such as: lemon yellow is a green-yellow and magenta is a blue-red.) Notice that it is easier to see the color biases of each tube when they are grouped together because you can compare the hues. Isn’t fun to see all of those beautiful blues?
When I am teaching color mixing I do not bring up the topic of temperature, because students have difficulty thinking of blue as being either ‘cool’ or ‘warm.’ They can do it with the other two primaries of yellow and red, but not with blue. I have learned to first teach students to SEE the color bias in a blue tube of paint.
Nearly every tube of blue has a color bias of green or red. There are very few pure tubes of blue. By the way, some painters consider cobalt blue as a pure blue, but due to manufacturer’s prerogatives, this does not hold true from one brand to another. It is helpful to paint a chart of all of your blues like the one above and compare because some cobalt blues carry a red bias and some a green bias
So Why is it Important to Understand the Color Bias of Blue?
In this chart of blue swatches, I have painted the most common green-blues on the left – cerulean, phthalo and Prussian – and the red blue on the right – ultramarine – by two different manufacturers, Golden and Liquitex. 
Color Tip: Most tubes of blue paint carry a green bias. For some reason, there are only a couple of red-blues and this is true across all media – oils, acrylics and watercolors.
There are two main reasons why it is important to know the color bias, not if blue is warm or cool.
1. When you are wanting to create a sense of depth in your painting, we know that warm colors come forward and cool colors go back. Within the subset of warms and cools, for example, if you are painting red flowers, you want to use warm-reds for those flowers or petals that you want to be in the foreground or to come toward the viewer. Subsequently, you would use your blue-reds or ‘cool’ reds for those you want to push back.
So what to do with blues? When you look at this color study of blues using a green-blue and a red-blue, which comes forward to you? Are you sure or are you just repeating what you have heard someone state? Because we all see slightly differently, we cannot agree when it comes to blue.
Which blue comes forward to you? The one with the yellow bias or the red?
The important thing to do is to be consistent within your painting. If you see red-blue as the blue that comes forward, then you want to use green-blues in your background or where you want the blue to feel behind something. It is too visually confusing if you flip them back and forth within a painting. You need to use the blues with conviction. Decide which blue – the green-blue or the red-blue – come forward and which goes back and then stick with it.
2. The second reason comes into play when you are mixing color. When you know the color bias of your blue, then you will be successful in the color mixtures you want. It will be easy to mix a bright green or a dull green if you mix with the correct blue.
In this color example, I am mixing green. Notice that the greens are brighter when I use two different green-blues in the top two rows with the same green-yellow. Then notice how the green is slightly duller because I mixed a red-blue with the same green-yellow (It is more evident in real mixing versus this digital image.). In the last row, I mixed a red-blue with an orange-yellow and the resulting green is duller.
Can you see how knowing the so-called ‘warm’ or ‘cool’ blue does not help when it comes to mixing color? It is less confusing when you leave the topic of temperature out of the conversation and do not ask if blue warm or cool.
Color Tip: Knowing the color bias of all of your primaries is the secret to frustration free color mixing!
Can you agree that the temperature of blue is not as important as knowing and seeing the color bias of a blue?
Want to learn how to assess the color bias of your paints and to release your joy of color mixing? Learn more about my online video course at Acrylic Color Mixing Made Easy! Note, that I use acrylics in this course, but the principles apply to all media.
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Carol – this is a wonderful article and analysis …. thnak you for your generous sharing on the public Internet!
Sincerely
Brenda Kelliher (was at Alyson’s workshop in Golden CO 18 months ago, met you there …and have been a fan ever since!)
Hi Brenda! You are quite welcome and thank you for your kind words. They are also words of encouragement which are warmly appreciated. I do not remember where you live….will you be at Alyson’s Office Open House on July 9th?
I found this about the blues extremely helpful. Thanks you.
Linda, So glad to hear it. Thank you for letting me know.
I have felt confused about the “temperature” of blue because, to me, blue with a green bias feels warm and blue with a red bias feels cold. From what I’ve heard most other artists say, this is backwards, but I guess it’s just a difference in the way I experience color. It is helpful to disregard the temperature and concentrate on the bias. Thanks for the tip.
Glad to help Chris. It is confusing. Stick with what works for you and how you SEE your colors.
When thinking about temperature you also run into the issue of whether red or yellow is the warmest primary color. I always assumed yellow was warmest but ended up in a “heated argument” with a friend who Insisted that red was the warmest color – and that red is always at the top of the color chart – not yellow. If red is actually considered warmer then yellow, then a green blue would be colder than a red blue.
The only thing that saves my brain in this argument is that if you see the absolute coldness of a glacier, that ice is pretty much a nice pthalo blue. It doesn’t get much colder than a glacier!
I Misspelled my name – oops – Carpenter, not Caroenter!
Yes, I agree that green blue is the colder that red blue. However, not everyone agrees as I stated.
BTW, red is NOT always at the top of the color wheel. Nearly all of the color wheels I use and create, I put yellow at the top. It is much easier to understand, starting with the yellow representing the sun. I won’t go into it further at this time, but the color wheel often has yellow at the top. In reality, it doesn’t make that much difference where a color is situated, just so a person understands the importance of it.
Thanks for your comments!
What a great post! Thank you. I really started to see the colors inside the blues after a minute or so, I didn’t see them at first but then they came out , I really liked the way you presented the swatches, we are so lucky today to have access to wonderful teachers who share their knowledge on the web. Thank you again
You are welcome Vincent! Thank you for your comment. Some how I did not see your comment until now. 🙁
Wow, fantastic blog layout! How lengthy have you been blogging for?
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Thank you! I have been blogging for several years. Feel free to spread the word and subscribe!