Earth is often known as the ‘blue planet’, and blue is used to represent the air we breathe and the water we drink. Blue is the colour of loyalty, holiness and virtue, but it’s also linked to deadly diseases and depression. And blue is the colour of uniforms, adopted by both the Navy and generations of denim-clad teenagers.
![Poster for modern housing](https://images.prismic.io/wellcomecollection%2Fe1ac0c12-98f9-4f3e-8e76-43e16b3c5668_air.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
In the days of heavy urban smogs, clean, fresh air was a major health issue. As this campaign for modern housing shows, the promise of blue skies was as much about what you left behind as having a shiny new house to live in.
![Advertisement for a Burroughs Wellcome inhaler.](https://images.prismic.io/wellcomecollection%2F5d0bf6dd-ad11-4d70-b32c-9df70a57adaa_inhaler.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
Not surprisingly, blue is the preferred colour for adverts about asthma and bronchitis and lung diseases. "Use my product and it’ll be like breathing clean, fresh air" is the message they convey.
![AIDS poster about water based lubricants](https://images.prismic.io/wellcomecollection%2F3f5973f7-db2d-4f82-90f6-069d3f61b9f4_water.jpg?w=780&auto=compress%2Cformat&rect=&q=100)
From swimming pools to water-based lubricants, blue says water. Like the rivers and lakes, water-based products are natural and good for your health.
![Player's cigarettes advertisement with sailor's head](https://images.prismic.io/wellcomecollection%2Ffbbb72b4-d3c5-455f-81ec-701daf210581_uniforms.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
As well as linking cigarettes with blue skies and seas, this advert also features a sailor in a traditional navy blue uniform. The British Navy adopted a blue uniform for officers - then called marine blue – in 1748. By the 18th century blue military uniforms were everywhere. 'True Blue' is the colour of officialdom, associated with loyalty, calm and harmony. The flags of the United Nations and the European Commission are both blue.
![Poster of a woman breastfeeding a baby](https://images.prismic.io/wellcomecollection%2Ff483f6dc-815f-4614-a66e-5451d542f6da_madonna.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
In the 12th century the Catholic Church decreed that the robes of the Virgin Mary should be painted with ultramarine - a blue pigment based on semi-precious lapis lazuli and imported from the mines of Afghanistan. By the Renaissance, blue was established as the colour of holiness, humility, virtue – and wealth! Good ultramarine was more expensive than gold. These associations persist, even in modern depictions of the mother and child.
![Drawing of a small child with cyanosis and measles](https://images.prismic.io/wellcomecollection%2F78111e6d-6472-4d3e-9287-b0b39d982c39_cyanosos.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
Cyanosis literally means the blue disease or the blue condition. The obvious symptom of cyanosis is bluish skin due to deoxygenation of the blood. Acute cyanosis can be as a result of asphyxiation or choking. In heart conditions, it’s also a sign that the heart is not pumping blood effectively, and this is the cause of 'blue baby syndrome'. Cholera was called the Blue Death because acute dehydration in the later stages gave victims' skin a bluish tinge.
![Caricature of a depressed man surrounded by 'blue devils'](https://images.prismic.io/wellcomecollection%2F522aefa5-fae2-48d3-b2a0-92023b3e0807_devils.jpg?w=1338&auto=compress%2Cformat&rect=&q=100)
Feeling blue and having ‘the blues’ are familiar terms for depression and melancholy. They probably derive from the term ‘blue devils’, which was in use as far back as the 18th century. “I feel a fit o them cursed blue devils coming across me” says the dejected looking man in this 19th century print. Another print suggests a link between the unhealthy bluish palour of illness and low spirits. Whatever the origin, it’s another association that persists. After the suicide of his friend, Picasso literally entered a Blue Period (1901–1904) when he used blue tones almost exclusively to create a melancholy mood.
![AIDS Public Health Poster](https://images.prismic.io/wellcomecollection%2F299e96cf-51e4-43f4-a15e-071323678d2f_indigo.jpg?w=1000&auto=compress%2Cformat&rect=&q=100)
The deep blue shade of indigo has its own band in the rainbow. It’s also the name of a plant that sparked several international trade disputes. The European clothing industry used woad to make a blue dye called pastel, but by the 17th century, it was superceded by a superior dye based on the indigo plant, exported from colonial India. Natural indigo dyes were themselves replaced in the early 20th century by the synthetic dye indanthrone blue. Around the same time, Levi Strauss produced his indigo denim work trousers. In 1935, blue jeans were raised to the level of high fashion by Vogue magazine and rapidly became the uniform of the young (and young at heart) everywhere.
About the contributors
Lalita Kaplish
Lalita is a digital content editor at Wellcome Collection with particular interests in the history of science and medicine and discovering hidden stories in our collections.