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Blue, the relaxing and peacefully colour of the sky and the sea

Updated: 5 days ago

Blue paint
Image by Lorena Martinez from

This is my new stop during my journey to discover every chromatic colour of the colour wheel. In this post I will talk about the colour "Blue", which is the colour of  sky, sea and water that we automatically associate to freshness, peace, relax.

Blue is one of the three primary colours in the traditional subtractive RYB colour mixing model, as well as in the additive RGB colour mixing model. It lies between violet and cyan on the spectrum of visible light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colours; azure contains some green, while ultramarine contains some violet.

In this post I will talk about the origin of the colour name itself, its meaning in psychology and symbolism, the most important pigments and shades for art.

Where does the colour name "blue" come from?

The modern English word blue comes from Middle English “bleu” or “blewe”, from the Old French “bleu”, a word of Germanic origin, related to the Old High German word “blao” (meaning 'shimmering, lustrous').

What does the colour blue mean in psychology?

Blue is the timeless colour of the sky, the sea and of the infinite space. According to the contest, it can a light blue can symbolize freedom, immortality but also calmness, relaxation, stability, reliability, peace and spirituality (lighter to turquoise shades of blue). On the contrary a darker blue can be associate to both positive concepts such as knowledge and authority and, in case of indigo blue shades, to more negative concepts such as fear, threat and frighten (thinking of the deep ocean during a storm). Sometimes it is connected to consciousness and intellect.

What are the most important blue pigments?

Blue pigments, indicated with the letters PB in the The Color of Art Pigment Database, were originally produced from lapis lazuli, a very expensive blue stone mined in Afghanistan, which is also the raw material to get ultramarine blue.

Today blue pigments are produced in synthetic form and the most important are:

  • PB15 Phthalocyanine Blue

  • PB16 Phthalocyanine Turquoise

  • PB27 Prussian Blue (only in watercolour paint)

  • PB28 Cobalt Blue

  • PB29 Ultramarine Blue

  • PB35 Cerulean Blue

  • PB36 Cobalt Chromite

  • PB60 Indanthrone Blue

What are the most common shades of blue?

Blue Shades
Blue Shades from the "Colour Thesaurus" by Ingrid Sundberg

Phthalo Blue

Phthalo Blue (PB15), also called phthalocyanine blue, is a bright, crystalline, synthetic blue pigment produced by mixing copper and phthalocyanine. It is the best colour in terms of lightfastness, tinting and covering strength. It was discovered in 1927 and comes in eleven variations. Phthalo Blue can have either the reddish shades (C.I. Pigment Blue 15:0, 15:1 und 15:2, less reddish, and 15:6 with a stronger red component) or greenish shades (C.I. Pigment Blue 15:3 und 15:4). (Watch more)

Prussian Blue (also Berlin Blue, Brandenburg Blue, Parisian and Paris Blue)

Prussian Blue (PB27) (former commercial name Berlin Blue) is one of the very first synthetic blue pigments ever known. It is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts and named after the colour used in past for the uniforms of the Prussian army.

It was accidentally created in Berlin by the Swiss paint maker Johann Jacob Diesbach in 1706, during its trials to produce a red cochineal dye by mixing blood and potash. Since then, due to its stability, lightfast and tinting properties, it has been used as substitute to the very expensive ultramarine blue.

Unfortunately, due to its high sensitiveness to alkaline substances, it can’t be mixed pure to an acrylic polymer to create acrylic paints and it is usually substituted by a mixture of phthalo blue, black and violet pigments.

Cobalt Blue

Cobalt blue (PB28) is a pigment with mineral origin made by Cobalt blue is a blue pigment made by sintering cobalt oxide with aluminum oxide (alumina). It is a light shade of blue (less intense than Prussian Blue) that can have either a red or a green shade. In the past it was employed to colour glass and Chinese porcelain and nowadays, due to its brightness and “eye catching” feature, it is used for many corporate and branding logos.

Ultramarine Blue

Ultramarine Blue (PB29) is a blue coloured pigment obtained by lapis lazuli in powder form. The term “ultramarine” derives from the Latin term “ultramarinus” meaning “beyond the sea”, because during the middle age the necessary gems were imported in Italian from Afghanistan.

The natural pigment is very sensitive to discoloration and very expensive. For this reason it has been substituted with a syntethic version to produce the paints.

Cerulean Blue

Cerulean Blue (PB35) is a blue-green pigment consisting of cobalt stannate and presents a shade of blue ranging between azure and a darker sky blue. The word is derived from the Latin word caeruleus ("dark blue, blue, or blue-green"), which in turn probably derives from caerulum, diminutive of caelum, "heaven, sky". At first the colour was known under the name of Höpfner blue, from its developer the Swiss chemist Albrecht Höpfner. Then the term Cerulean Blue started to be used to indicate the colour based on cobalt stannate.

Today, the term Cerulean Blue is also used to market the pigment cobalt chromate (PB36), even thou this is darker and greener than the cobalt stannate version. For this reason, and to distinguish it from the cerulean blue based on cobalt stannate, the cerulean blue based on cobalt chromate is called "cobalt turquoise".

Royal Blue

Royal Blue is a deep and vivid blue variation produced with the pigment PB15:2 (RS). At first the term “royal blue” was used to identify a deep blue with red shade, similar to the one used under the reign of Luis XIV by royal body guards and court employers. Later it became popular in England during the reign of Queen Charlotte to identify a dark blue shade that should have to be used to dye her robe.

Indanthrone (or Anthraquinone) Blue

Indanthrone Blue (or Indanthrene), is a dark blue compound that, as a pigment (PB60), is used in many paints. The name comes from the union of two words: Indigo and Anthracene.

Indigo Blue

Indigo Blue is a colour between blue and violet and one of the chromatic colours of the rainbow identified by Isaac Newton in the middle of the 17th century.

The name comes from the Latin word indicum (Indian) because the plant used to produce it (indigo) was imported in Europe from India.

In the electromagnetic spectrum it is placed between 420 and 450 nanometers, which corresponds to a blue with a violet bias.

Throughout the years there has been many scientists who discussed the exact position of the colour and recently they have come to the conclusion that the colour should be considered as a blue shade more that a violet one.

Final words.

As we have seen, blue is a very particular colour, full of history, with wonderful warm and cold shades. Is blue your favourite colour?

Thank you for reading. If you like the post, leave a like, a comment and don't forget to follow my blog, Instagram and Threads and share the content on your social media.

In my next posts I will have a look at the fresh colour on the wheel: Cyan/Turquoise.

Until then I hope you will have a great creative day!



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