I have been in love with Violet for more than 40 years. Violet over the centuries has served as the color of royalty and deity because of the cost to acquire the beloved color. Thankfully today it is easily acquired and easy to mix as a painter if you know the correct colors of red and blue to combine to create it.
For any complete beginners out there that do not know this: Violet is a combination of the colors blue and red. But you cannot just combine any blue and red together to create the engaging color that so many painters love. When mixing violet, one must consider both warm and cool colors and the color science behind their combination to determine what works and what doesn't.
First, let's have a look at blue. Blue comes in (simple terms) three categories: Warm Blue, which is Ultramarine Blue; Primary Blue which is Cobalt Blue; and Cool Blue which is Cerulean Blue and Phthalo Blue. Now let's take a look at red. I'll classify red in two categories: Warm Red, which is Cadmium Red, (medium or deep) the most popular type of warm red; Cool Red, which is Quinacridone Magenta, Alizarin Crimson and Permanent Magenta.
The best violet is made from Warm Blue (Ultramarine) and Cool Red (Quinacridone Magenta, Alizarin Crimson and Permanent Magenta). Why? Color science tells us that warm blue is a mixture of blue with red in it. The red helps to warm the blue. Cool Red is red with blue in it. The blue helps make the red cooler. If violet is a mixture of both blue and red, and both the warm blue and the cool red contain blue and red, then each of those colors is already halfway to violet. When they combine, they make the perfect violet - one that can be mixed with more red to create a red-violet or mixed with more blue to create a blue-violet.
So what happens if we completely turn the tables and mix the opposite colors together - meaning Cool Blue and Warm Red? Color science says that Cool Blue is blue with green mixed in it to make it cooler. Warm Red is red with orange mixed in it to make it warmer. When the two are mixed together the blue in the cool blue cancels out the orange in the warm red and the green in the cool blue cancels out the red in the warm red (because they are complements that mix to gray), so the resultant mixture is gray, or depending on the paint brands you use, possibly a heavily grayed violet.
As you will see in the accompanying video, I also mix together ultramarine with cadmium red, cerulean blue with quinacridone magenta and cadmium red as well as cobalt blue with quinacridone magenta and cadmium red. The results show that all of the blues mixed with cadmium red produced gray. All of the blues mixed with quinacridone magenta produced a different violet. The mixture of cerulean blue and quinacridone magenta produced a blue with only a faint hint of violet. The color science tells us that the green in the cool blue cancels out the red in the cool red, thus leaving only blue as the resultant color.
Try these mixtures in your studio - it is the best way to learn about color - mix it and see what happens. If you are able to understand the concepts and master the implementation of this color mixing in your work, you will be a better painter. I guarantee it!