Does this particular shade of blue have a name?

How lightfast a color is is determined by what you are using. Inkjet printer ink, oil paint, fabric dye, etc. all have different colors that are more lightfast than others. Can you tell what kind of ink was used to create the poster?

My understanding is that the cyan ink used in 4 color printing is the last to fade simply because the other colors absorb UV light more than the cyan does. The UV light packs higher energy than other wavelengths, and so it breaks down the pigments that absorb it.

Any ink that tended toward the blue end of the spectrum would survive UV bombardment better than “warmer” colors. Many blues have a touch of red in them though, and that would fade, slightly altering the color. Cyan does not.

@Kayak8 Not sure.

@thorninmud So I’m seeing cyan because it’s the most lightfast of the inks used in typical 4 colour printing? And not necessarily because it’s the most lightfast colour in general?

Do you have a photo of the color you are referring to?

Theoretically, the closer you get to UV on the spectrum, the more resistant that color would be to fading from UV exposure, because it would reflect rather than absorb UV. So if you look at the spectrum of visible light, the color at the very extreme of the “violet” end would be the most fade resistant.

Example 01

Example 02

Example 03

Example 04

@thorninmud That makes sense to me.
Though it makes me wonder why there isn’t more violet left on sun worn items?

There wouldn’t be any violet because violet is a mix of cyan and magenta, and magenta fades first. So any colour that uses magenta in it’s mix would be lost; reds, oranges, browns and purples.

I would call that sky blue.

Robin’s egg blue

Oh, I didn’t think to include a pic. Good thinkin’, @marinelife.
Sky blue.

What we usually call “violet” is not actually a spectral color. “Color wheel” violet is obtained with the addition of a magenta component (which, in turn, contains red), and that red component will fade (as @downtide said).

Check this Color Chart out…

For Bonus Question…
The technical term for color fading is photodegradation. There are light absorbing color bodies called chromophores that are present in dyes. The color(s) we see are based upon these chemical bonds and the amount of light that is absorbed in a particular wavelength.

Ultraviolet rays can break down the chemical bonds and thus fade the color(s) in an object – it is a bleaching effect. Some objects may be more prone to fading, such as dyed textiles and watercolors. Other objects may reflect the light more, which makes them less prone to fade. -> loc.gov/rr/scitech/mysteries/colors.html

Have a read about CMYK Color Model, too.

In copy stores, that color is called Astrobright Blue or Cyan Blue.

[mod says] This is our Question of the Day!

Great information, guys. Well done!

You are not talking about a particular shade of blue—you are talking about the printing process itself. Printing is typically a CYMK process and colors are laid down in that order. Cyan screen is printed first, magentascreen second, yellow is third, and last [top] is the black screen. What you are seeing with faded posters is the layers fading from top down, with the cyan being last to go.

@augustlan Neah. More like Answers of the Day.

@anartist That’s interesting. Why isn’t cyan printed last to protect the other colors that may be prone to fading with UV exposure?

Because it has no special UV powers that I know of. Also, except for the black [which is usually a very thin halftone screen to just enhance the colors], the colors are printed dark to light.

Besides, th different colors cover different areas of the page. The cyan would only be printed in the same place as magenta when a bluish or purplish color was sought and only be printed with yellow when shades of green were sought.

If cyan has any UV properties it would be only its relative closeness to the ultraviolet edge of the spectrum because it is a component of blue/violet [along with magenta]. Magenta also is a component of blue/violet. Magenta also is a component of red. Does that then place it place it near the infrared edge of the spectrum as well?

I’d add a Wikipedia link to the CMYK printing process, but that would be “content farming” wouldn’t it?

And for the inverse of this Q:
Anyone notice that their old color photos, say from the 50s, have gotten red?
Similar reason, different process. CMYK is a printing process based on reflective light, Photography [RGB] is based on transmitted light. The emulsion layer of the colors is red at the bottom, green next, and blue on top. Therefore, the red is last to go. Interestingly enough, the color filters used are cyan [lets red pass through], magenta [lets green pass through] and yellow [lets blue pass through].

Such a lovely harmony.

@anartist While that sounds right to me,
it doesn’t feel right to me.
At least not with posters.

I dont think I’ve noticed posters fading in that order.
(Loss of black, Yellow, Magenta, then Cyan last.)
Plus, the Cyan hangs around long after.

Though maybe that works for photographs though.
(Loss of Blue, Green, then Red last.)
Unlike Cyan, Red will also fade.

Maybe the difference has to do with chemistry like Kayak8 mentioned?

@Nimis Look at the posters as I had done for many a year as the printer posters replaced the hand-silkscreened ones [these never had a fading problem] we used to post along the fence to the Museum of American Art, Smithsonian, in the 70s. First they get washed out, then they lose the yellow and look too much red/blue/cyan and finally—cyan.