Making a Blue Cooler or Warmer
Creating a secondary color such as purple by mixing red and blue is very tricky because you cant just use any blue or red. In fact, if youre not careful, you might unintentionally be mixing all primaries of the color wheel—red, blue, and yellow. Where does the yellow come from? Yellow comes in the warmer blue, and in the warmer red. Therefore, it makes sense that the purest purple would come from the cooler red and the cooler blue.
When mixing blues and reds to make purple, ultramarine blue and alizarin crimson give the purest purple. When you use ultramarine blue and cerulean blue that ultramarine blue tends to recede and cerulean blue tends to come forward, as is the general rule for cool and warm colors.
For resolving this matter, it is best to try your own hand at mixing colors, using different combinations of blues and reds to create the purest purple you can. For example, try mixing cerulean blue and ultramarine blue with cadmium red or alizarin crimson in different combinations. However you decide to classify your blues, the important thing is being able to control what they do on the canvas, how they mix with other colors, and how they relate to adjacent colors.
Note: Cobalt blue is generally considered to be primary blue and the most “pure blue.”
What Does “Warm” and “Cool” Mean?
The temperature of a color is always a relative measure; a color cant be cool or warm by itself, it can only be “cooler than” or “warmer than” another color. What establishes that relative coolness or warmth is a matter of opinion.
Theres no argument about the location on the color wheel for the different blues. For example, on the traditional color wheel, ultramarine blue is closer to violet, while phthalocyanine and cerulean blues are closer to green. Violet is closer to red, and green is its complement on the color wheel, so you could decide that ultramarine is warmer.
On the other hand, if blues bias is towards green, then it must also contain a bit of yellow, since blue and yellow combine to make green. And yellow is indisputably a warm color (at least compared to other colors). Also, since ultramarine blues bias is purple, that would make it a cooler color since purple is the complement of yellow.
However, the issue is by no means settled. Many established artists have decided opinions of their own.
In her article “Warm or Cool? Ultramarine Blue vs Thalo Blue,” colored pencil artist Sharon Hicks reports that years ago she was taught that ultramarine blue was cool and phthalocyanine (thalo) blue was warm, but she has also more recently come across articles saying the opposite. She believes that is because instead of using the traditional color wheel, more people today use the color spectrum, which is the conversion of the visible light spectrum into a new color wheel. On the cool end of the color spectrum, violet is cooler than green, and so the violetish ultramarine would be considered cooler than greenish thalo or cerulean blues.
Herein lies one of the issues that I find fascinating with color. So much of how we see is in our perception, and is not an objective recording of s like a camera. The issue I am referring to here is whether or not there is any argument as to which blue is warm and which is cool.
Blue is the purest and the “coldest” of the cool colors as it is the only one which is a primary color. Just as with warm colors, within the overall family of cool colors, there are still warm and cool variations. There are warm blues and cool blues, but they are all cooler than any warm color could ever be.
However on a personal level, Phthalo Blue just “looks” warm to me. Its subtle green undertones make me think of tropical beaches and clear summer skies. Ultramarine just “looks” cold. Like shadows on snow in the winter. However as I said, there are many color theorists who say just the opposite. They are not wrong, it is just that their perception is different.
If you simply boil it down to looking at the color wheel as only consisting of mixes of the three basic primary colors, then what you are really saying here is that Ultramarine leans towards red and Phthalo Blue leans toward yellow. Of the two warm colors, red and yellow, yellow is the warmest and so the blue that leans toward yellow (Phthalo) is warmer than the blue that leans towards red (Ultramarine).
Two of the most popular and common blues used on an artist’s palette are Phthalo Blue and Ultramarine (There is also Cobalt Blue but we’ll get to that in a minute). One is a warm blue and one is a cool blue…but which is which? There are different schools of thought on this depending on how you see and use color. Look at the sample below and decide for yourself which is which…
Which is warmer Ultramarine Blue or phthalo blue?
What is the difference between phthalo blue and Ultramarine Blue?