5 Cerulean Blue and Quinacridone Magenta
I like to use Cerulean Blue for painting skies with watercolors. Sometimes clouds have a purple tint to them so I add a small amount of Quinacridone Magenta to the Cerulean Blue.
You can also use Cerulean Blue to mix a vibrant purple. In the example above, I use Cerulean Blue Hue and Quinacridone Magenta. Anytime you see the word “hue” in a color name, that means it contains substitute pigments. The results are similar to what you can achieve with real Cerulean Blue.
6 Cobalt Blue and Quinacridone Magenta
I have both Phthalo Blue and Ultramarine Blue on my palette but one problem with them is that they’re very dark. If you want to mix sky blue I have to make a lot of adjustments.
Phthalo Blue is very dark when you use it straight from the tube. It has a lot of tinting strength, a small touch of it will affect a large volume of paint. Cobalt blue is much lighter so you can mix sky blue just by adding white to it.
You can use Cobalt blue to make some very nice purples. Just add some Quinacridone Magenta to it and you can get a variety of purples from this color.
Why Red and Blue Doesn’t Make Purple
There are numerous color wheels that show that you can mix bright purple from red and blue. The red and blue they use in these illustrations are similar to Cadmium Red Medium and Ultramarine Blue.
If you mix red and blue, you get a muddy brown color as shown below. It doesn’t look anything like the purple on the color wheel. You may assume that adding more Ultramarine Blue will turn it purple, but it just makes it darker. The reason why it makes brown and not purple is because the red contains yellow.
Red is not a primary color, it’s a mixture of magenta and yellow. Some artists classify Magenta as a cool red, but I disagree. Magenta is a primary color and red is the secondary color. You can mix red by adding a small amount of a transparent yellow, such as Hansa Yellow Medium, to Quinacridone Magenta. The red is transparent, but the hue is close to Cadmium Red Medium as shown in the illustration below.
You can use Magenta to mix orange, red, and purple. There’s no shade of red that you can use to mix such a wide range of colors.
If you’re interested in mixing red then you may want to read my article How to Mix Red.
Surprisingly, magenta is often missing from most color wheels. Since it’s a primary color, you can’t mix it from any other colors.
Some color wheels have magenta on them between red and blue. This suggests that you can mix magenta from red and blue, but that’s not correct. It’s misleading so I don’t recommend working from these color wheels.
The point is that it’s the yellow in the red that makes the purple turn brown. An experiment you can try is to mix a yellow with purple. It creates a muddy brown color. Below is a mixture of Cadmium Yellow Medium and Dioxazine Purple. Notice that it’s not too different from the brown that I created by mixing red and blue.
How Do You Turn Purple Into Blue?
If you want to mix a shade of blue that’s similar to Ultramarine Blue, you can add Phthalo Blue to the purple as shown in the above photos. The top photo is pure Dioxazine Purple. The second photo is a mixture of Dioxazine Purple and Phthalo Blue. As I continue to add more Phthalo Blue it starts to look very similar to Ultramarine Blue as shown in the third swatch.
The color swatch at the bottom is pure Phthalo Blue, direct from the tube. You can’t mix Phthalo Blue because it’s a primary color.
In order to turn Dioxazine Purple into Phthalo Blue, you would have to subtract the magenta from the purple, which is impossible. This is like trying to remove salt from a batch of soup. You can always add more salt to the soup, but you can’t take it out. The best you can do is to dilute the soup with water to make it taste less salty. The same is true with adding blue to purple. It will shift the color towards blue, but it will still have a purple tinge to it.
An obvious point to make here is that if you have phthalo blue to add to your purple, then why not just use the phthalo blue instead? This is especially true if you have a large batch of purple that you want to shift towards blue. It would require a large volume of blue to have any impact upon a large batch of paint.
In that case, it’s probably best to put the purple aside and start over. That’s the nature of color mixing. Sometimes you make a mistake and have to start over.