I'd confidently say that these days many people haven't much of a clue about the full range of the shades of blues that their eyes can actually see and if they did then they'd be rather surprised!

Unless you're a gardener or a flower grower who specializes in blue flowers or a lepidopterist specializing in blue butterflies you'll have spent most of your life looking at a very limited range of blues. You many think you've seen many shades of blue and you probably have except that most of the blues you've seen have come from a very limited range of dyes and pigments—in essence, your normal viewing experience of blues comes from this rather limited subset. These you'll encounter as pure dyes or pigments or various mixtures thereof. To provide light shades of blue white is added and to make the blue hue appear 'richer' small amounts of other colors, typically red, are added (it's a form of cheating/fooling the eye so to speak).

Right: that seems like many shades of blue available—and it is—but each of this limited range of dyes and pigments has its own intrinsic characteristic spectral response, thus each blue has an underlying 'characteristic blue' appearance common (and often recognizable) to all those shades and intensities. The trouble is that our eyes are remarkably discerning and they can see a much larger range of blues that exist outside our present commonly available range of blues.

Superficially, there seems to be a sufficiently large range of blue dyes and pigments available for our needs; for example, to name the more common, Azo dyes (diazo blue), indigo (jeans blue), Prussian blue, lapis lazuli (ultramarine), cobalt blue, copper-based blues–Egyptian blue, azurite, etc. However, the range of available blues is quite limited when one takes into consideration the physical and chemical properties of each dye and pigment, as sufficient numbers are either unstable and or are not suited to the industrial processes (printing, dying plastics, clothes dying, etc.), or they're rare and hellishly expensive (lapis lazuli for instance).

Another reason many haven't experienced the full spectrum of blues the eye is capable of perceiving is that blues aren't all that common in nature. It's worth taking a few minutes to watch this YouTube video titled "Why Is Blue So Rare In Nature?" https://www.youtube.com/watch?v=3g246c6Bv58. (Given the fact that blue is so rare in nature, what surprises me is the unanswered question of why the human eye has nevertheless thus evolved to be so discerning in the blue region—anyone any ideas?)

This brings me to the next point, which is to mention how a curious person can easily check his or her eyeballs out on a range of extended blues that are outside those that we normally encounter (à la those listed above). Several decades ago, I attended an electronics engineering conference where much of the subject matter was on the colorimetry of color television and I was thinking about the fact that the color gamut of television was limited by the comparatively poor performance of the blue phosphor (amongst other things). Not being in my home city, between conference times I found myself occupied wandering through the nearby park where to my surprise I stumbled across a conservatory full of brilliantly colored cineraria flowers (Pericallis × hybrida), many of which where dazzling shades of blue—blues that were way outside the color gamut range of normal color film, color TV, printing and dyed objects.

As colorimetry has occupied part of my career for years, I'm very perceptive of color and coming across a huge variety of brilliantly colored cineraria was quite an eye-opener [duh]. Cineraria come in all sorts of dazzling colors but those that I'm principally interested in are the blue ones. There are two interesting properties of many (but not all) cineraria flowers and they are that the color of their petals is most intense (saturated) at their outermost extent and that this color progressively and completely fades to pure white near the center of the flower; and second, there is a phenomenal range of hues and levels of saturation within each color group (with the blues being the most spectacular). (If you're unfamiliar with cineraria, do an image search on "blue" + "cineraria".)

The important aspect of seeing cineraria in public gardens' conservatories is that one can see, compare, and experience this vast variety of colors that would be very rare to experience elsewhere. Whenever I'm in a city for the first time, I'll often check to see if there's a cineraria conservatory there. Of the best two conservatories I've come across one is in Longwood Gardens, Kennett Square, Chester County, PA, https://plantexplorer.longwoodgardens.org/weboi/oecgi2.exe/I... and the other in Fitzroy Gardens, Melbourne, Australia, https://vimeo.com/288066051, however I'm sure there are many more elsewhere. As I've stressed, the blue colors you'll see in the cineraria images in these links is only a rough guide to what you'll actually see in real life—the artificial colors just can't match the real thing! (If you intend to visit a cineraria conservatory then time it to be when the plants are in full bloom and do so on a bright day when natural daylight is at its peak.)

My commentary about cineraria isn't to put a scientific measure on what I've said but only to demonstrate that "A Good Blue Is Hard to Find" and it's always been so throughout history—and that you can demonstrate the fact for yourself just by looking at these flowers. Incidentally, the quoted text in the last sentence is the title of a book review in Scientific American by Peter G. Brown of Bright Earth: Art and the Invention of Color by Philip Ball (SciAm ISSN 0036-8733, Vol. 286, Nº 3, 2002, pp 98-100). There's more about the book below.

Finally, this brings me to the point about YInMn blue. I recall the announcement of its discovery in 2009 (as any new blue is a big deal). There is no doubt that it's sorely needed and that it will be a most welcome addition to the range of available blues (As yet, I've not seen it in the flesh but I'm eagerly awaiting the experience). There's no doubt that it will extent the range of blue hues and add considerable vibrancy to the color (soon expect to see important extensions (new numbers) to the blue range of Pantone colors). ;-)

While YInMn blue will go along way to improving the 'reproducible' blue spectrum, it nevertheless won't solve the blue problem completely. For starters, it's only useful for printed material and coloring physical objects, it doesn't help with the reproduction of electronic colors, TVs, displays etc. Also, there's still the need to give better vibrancy to the existing range of blues (ultimately, we still need to add vibrancy to the older [spectral] range blue dyes and pigments so as to balance them with the brighter, more vibrant YInMn blue).

If you're interested in the subject of color then the book 'Bright Earth: Art and the Invention of Color' by Philip Ball is an excellent place to start. The mentioned SciAm review isn't available on line but these two ought to suffice:

http://www.librarything.com/work/206920/reviews/68183903

https://www.theguardian.com/education/2002/jan/26/highereduc...

Note: I'm only familiar with the 2002 edition so I am unable to say whether Philip Ball has included the 2009 info about YInMn in his later 2010 and 2012 editions.