I'm old enough to remember a time before blue LEDs. Funny how they're everywhere now.

I make photo prints using the cyanotype process and a UV LED light source. It's a combination of old and new technologies with a very unique look. While the sensitizing solution contains cyanide, it's fine as long as you wear gloves (and don't drink it).

The artist Alphonse Mucha associated blue with the past: "Black is the colour of bondage, blue is the past, yellow the joyous present, orange the glorious future."

Blue of course is a cold color. Perhaps one of the less eccentric colors, and ubiquitous as the author mentions. So in line with the disappearance of color from modern design, it is one of the few remaining colors in our vision of the future.

The use of Prussian blue is rampant in most painting programs. The reason is that you are essentially getting two paints for the price of one. When applied thinly, it is light and saturated. When applied thickly it is almost black. Contrast that with cobalt blue, which looks the same pretty much however you apply it.

Alizarin crimson behaves similarly.

Painting with either of these pigments it is relatively easy to get superficially impressive effects.

As a painter and also a digital artist, I am always amazed by such physical dimensions of oil paint. Another example is the huge difference between zinc white (low in coverage, good for transparency, slightly cold), and titanium white (high in coverage, good with mixing with other pigments, more neutral).

> It is the most technological color, and I’m willing to claim that this is why it is usually, in science fiction and elsewhere, used to represent the future.

For me it is because of red- and blueshifting[1]. Far away galaxies appear both older and redder the further away they are, so red is the past. And if you go really fast, the forward view will be bluer, so in the sense that it is where you go, blue is the future. [1] https://en.wikipedia.org/wiki/Redshift#Blueshift

At the Smart Museum in Chicago [0] I've seen Yves Klein's coffee table which uses copious amounts of the iconic International Klein Blue pigment under the transparent surface, it's very striking.

[0] https://smartmuseum.uchicago.edu/exhibitions/building-enviro...

Shenzhen is not all futuristic blue all the time, as shown in the picture in the article. Most of those buildings have full RGB capability. Here's a drone video of Shenzhen at night.[1]

For the 45th anniversary of the Shenzhen Special Economic Zone last month, the building lighting and rooftop lasers were coordinated with a 12,000 drone show.[2] Mostly white, some blue tinge, red buildings on the more official messages. Not much green. That's Shenzhen looking futuristic on purpose.

[1] https://www.youtube.com/watch?v=1Vz3mP3iMiw

[2] https://www.youtube.com/watch?v=FDNkcKiD2Ow

A beautiful book by Michel Pastoureau, Blue: The History of a Color (2001), the same content as the article in book form.

https://www.amazon.com/Blue-History-Color-Michel-Pastoureau/...

In a similar vein: https://www.scienceabc.com/eyeopeners/why-are-blue-fireworks...

Blue fireworks look cool, but you almost never see them.

Fun fact about lapis lazuli/ultramarine: if you grind it too finely, it turns gray. A friend who has recreated many medieval paint pigments discovered this the hard way... Just another reason it is so complicated to produce.

The reason is that the crystalline structures that finely select for that narrow band of blue are destroyed. The same thing happens if you put an oil drop on water: at first brilliant rainbow bands of color are produced (from the selective reflections off either side of the oil, where the oil thickness is a multiple of the light quarter-wavelength). Then the oil spreads further, until it is less thick than a blue light quarter-wavelength, and it turns dark.

> Finally you have ultramarine! How much? I can’t find good numbers, but Claude estimates that the ultramarine production of all of medieval Europe was around the order of 30 kg per year

So we're at that stage ? Scott Alexander asking Claude for estimates on unknown stuff and quoting it on that. Gosh, I didn't imagine the lack of awareness of the limits of LLMs was this bad.

For a fun story on Prussian Blue, read the first chapter of Benjamín Labatut's When We Cease to Understand the World.

How do you manage to write an entire article on blue without mentioning methylene blue?

Obligatory mention of the Radiolab episode titled 'Colors' [1] - which among other things, talks about how the color blue appears in almost all world languages much later than other colors.

[1] https://radiolab.org/podcast/211119-colors

I paint with blue fairly often. I understand that it might be the hardest to create artificially, but it is done regularly in the modern world.

Could the fascination be due to psychological reasons, like blue light being linked to sleep difficulties? This seems to be the current world we live in, where blue light filters exist to help prevent sleep disorders. Perhaps because our skies are increasingly gray with pollution, so blue gives us hope of a future where our air is clean and without smog?

I might be missing the entire point of the article, but I feel that if I am, my fellow HNers are with me (even if they don't believe the same thing).

I love this quote:

"Cultural associations: ... Something something near-far Robin Hanson something something"

> Nobody has written about this more eloquently than Scott Alexander: >

For any subject, there is certainly someone who's written more eloquently about it than Scott Alexander (who's quoted using the word "pissed" here).