Phthalo blue (red shade)

Phthalo Blue

Some people hate it and others like it. I understand why so many don’t like it, it is so intense that it becomes difficult. It dries with lost of color joy. It is difficult to master.

But still, it is an important one to have in your palette. It is the only really primary blue color.

If you, like me, want to mix your colors (instead of buying ready-mixed), the color is a must, I think. It has a very clean hue, and it fits perfectly in the color wheel for a primary blue, it has excellent mixing properties, both in the violet and green direction.

It was accidentally invented in the 1920s and was produced as a pigment in 1935, then under the name monastral blue, a name that is still used. There are several variants of the pigment but this text applies to what is called red shade.

Color index name is PB15:1 some manufacturers use PB15:6. It is common for the color to be given other names, which is confusing. The most common alternative names are: Berlin Blue (should actually be Iron Blue), Helio Blue and Monastral Blue. Some manufacturers simply call Phthalo blue after themselves: Winsor Blue, Blockx Blue.

Phthalo blue, here mixed with Transparent Pyrrol Orange gives a neutral color mix


  • Extremely strong color pigment.
  • Phthalo blue is very transparent
  • The paint is very staining. The pigment grains are extremely small, which means that it sticks to all surfaces. (eg plastic pallets), the paint is staining.
  • Dries evenly and nicely, no granulation, perfect for smooth washes.
  • The paint loses a lot of saturation when it dries.
  • Excellent mixing properties.
  • Complementary color: red-orange.
  • Relatively cheap pigment, usually in the cheapest series from the manufacturers.
Phthalo blue is a transparent and strong color
The color blooms distinctly
The paint is staining, difficult to remove once it has dried
Wet on wet
Phthalo blue leaves a hard edge


Color index name: PB15: 1 | PB15: 6
Lightfastness: Excellent
Transparency: Yes, very
Staining: A lot
Granulation: No.

You may also like...

5 2 votes
Article Rating
Notify of
Newest Most Voted
Inline Feedbacks
View all comments
2 years ago

It’s a beautiful blue this one. Just a little goes a long way. If I’m in the right, when I mix it with a little bit of black, I get Indigo

Would love your thoughts, please comment.x