Am I right in thinking that colours that are pure cyan, magenta or yellow would come out brighter in print than colours such as green or purple for example? Due to the fact that they haven’t been mixed with anything else?
I once used a splash of pure cyan in a CMYK job and it came out looking really vibrant, I hadn’t realised it was possible to get such a colour in print without using Pantones.
Would the same be true of cyan and yellow?
I had never really thought about that before, but it sounds about right. In subtractive colors, each time another ink is added, the result is a darker color, even if it’s only very slightly darker, like adding yellow to magenta.
Then the brightest CMYK ought to be 0_0_0_0.
Well that’s 0% of all them which is nothing. Which isn’t CMYK. It’s just no ink.
This may be semantic, but the “brightest” color in CMYK is, potentially, the substrate. CMY inks are translucent, and although they are fairly vibrant on their own, the reflectivity or “whiteness” of the substrate is important to consider when “vibrant” output is the objective. Of course it stands to reason, as ink is applied to the substrate, its reflectivity is reduced.
Even if it were 0 01 01 0, that would be an extremely light screen tint, but I think thet OP was asking about solid color and, maybe, chroma, which reminds me of another thread from the past few days.
Well you’d print with C M Y K.
CMY should make black - but inks have impurities as such, black pigment was introduced for the K plate. I heard before people call this the Key plate (K) and I’ve heard before that it’s because RGB was already around so used K last letter of Black instead.
Black isn’t always the key plate, so that can be erronous.
Anyway - typically with a tint it would be printed with halftones. But a solid colour of Cyan would be purely Cyan. Which is just ink.
Same with MY and K.
Although large blocks of K can look a bit muddy - that’s why they put a rich black in for large blocks of black or anything over something like 36pt type or even 72pt.
Anyway - there’s no difference to CMY inks as there to Pantone inks - they are just inks.
When you combine a CMY in different combinations, the halftones used in print would converge with light, and send back to the eye the RGB required to view it.
So any combination of CMY is subjective to the viewer, as some people see different colours due to rods/cones in the eye.
And with impurities in the ink - the combination of CMY to form a RGB image in the eye, there’s going to be dullness anyway.
Plus you’ve to take into account the brightness of the paper, and if the paper is made with chemical treatments, such as Sodium Chloride which could discolour the paper over time (how long has it been on the shelf?) and this tint of yellow could affect the brightness of your inks. Or has the paper been treated with optical brightening agents?
When it comes to ink mixing with inks - there’s other things going on too, the humidity for example.
Well 0 0 0 0 is no ink.
You can have white ink. But that’s different.
Anyway, we all know what we all mean.
To provide a simple answer, yes, you are correct in your assumption that the brightest (saturation/vibrancy) would be either C M Or Y at 100% density.
If you look at a CMYK color space, you’ll find these primaries at the outmost corners of the gamut.
If you are only talking about plate printing, and only CMYK inks, then yeah, the CMY are probably the “brightest” colors you can get.
I work in digital, and for a lot of presses, that does hold true. Even the 6-color presses usually have only a light cyan and a light magenta. But there are machines out there now that expand the CMYK gamut by adding additional pigments such as orange, green and violet. No, don’t get sucked into the Pantone extended gamut book (if you make me buy that, I will be very…uh…disappointed…) But you can get some really vibrant colors if the print machine has the capability.
My whole problem with digital is ink droplet resolution, the actual dpi being laid down by the print heads. Most of these machines have varying productions speed which run from very fast draft (unsellable) mode to slow-as-grass-growing high-quality photo mode. Most printers run somewhere in between at an optimal speed and quality for their work flow. Some will vary that, depending on what their clients are willing to pay. But the faster a machine runs, the farther apart or larger-in-size those ink droplets are.
I can see the ink droplets in a 600dpi print at arms distance. And I do very well on a Munsell test. I’ve met others though that see these dots-combined-into-colors far differently, with a much greater hmmm…color fidelity maybe than I can. Of my clients that are extremely picky about color, between us, we suspect they just see things differently. These days, everyone is far more lax about color matches, but several years ago, man, they were hard to please. I remember an 18 color job (not all on the same print - museum, multiple panels in multiple exhibits, maybe 3-5 colors per panel) it took weeks and about a mile of test print ring-arounds to get them “right.” As long as I’m paid, I’ll do that all day long. But yeah, people do see those digital ink mixes differently.
And lighting will play a huge role too. When we do stage drops, the wrong gels, or these days, the wrong RGBA color mix in the LED stage lighting, will pop an ink color spectacularly. Magenta is often the culprit. Nothing like having your blue drop pop “pink,” LOL! Always good to have a good lighting tech around. 
Thanks! Simple is good 
Also thanks to everyone else for your replies
Stupid question here, but is pure cyan, magenta and yellow CMYK ink actually close to the ink used for the respective neon and/or retrospective colours? I know there’s also coating involved for neon colours, but since we’re talking about the brightest colours, I’m just wondering if there is a relationship between those.
Not really. The neon colors are spot inks outside of the CMYK gamut
It’s time for one of B’s annoyingly pedantic and long-winded physics lessons.
Fluorescent colors are the result of visible light being emitted by the fluorescent surface that is in addition to the light being reflected by that surface.
Here’s how it works.
Our brains interpret different wavelengths (or frequencies) of the electromagnetic spectrum as different colors. We can only see a portion of that spectrum, the wavelengths that extend from violet through the other colors and ending with red.
However, there are wavelengths of light that we can’t see just beyond the parts of the visible spectrum that we do see. Just beyond the violet end, there’s ultraviolet. Just beyond the red end, there’s infrared.
When light hits an object, the surface of the object interacts with the light and can do one of three things. The light can bounce off the object. The light can pass through the object. Or the energy that makes up the light can be absorbed by the object.
Different wavelengths of light interact differently with the surfaces they hit. A green surface, for example, absorbs most light wavelengths while reflecting those wavelengths we call green.
Those wavelengths absorbed by the atoms in that surface cause the energy levels of those atoms to increase. This is why an object sitting in the sun heats up — it is absorbing much of the light and converting it into thermal energy.
An atom is composed of a nucleus and one or more concentric electron shells (or layers) surrounding the nucleus. It’s the outermost electron shell (the valence level) that light initially interacts with. If the resonating frequency of the valence electrons corresponds to the wavelength of light striking them, those electrons will absorb the light particle (a photon), upping their energy levels.
The electrons in each layer of the shell must maintain certain energy levels to maintain their positions in its shell. The electrons in the outer shells must have a higher energy level than the electrons in the inner shells.
Sometimes the absorption of a photon will provide enough extra energy to bump up the electron to a higher shell level, which creates an unstable electron arrangement. To correct this instability, the electron releases the energy it absorbs and falls back to its previous shell level. The energy that’s released is emitted as a new photon with a longer wavelength than the original photon.
This absorption of a photon of one wavelength (or frequency) and its subsequent release as a photo of a slightly different (usually lower) wavelength is called fluorescence.
When fluorescence occurs in most of the visible spectrum, we don’t notice it. If an orange photon is absorbed and subsequently emitted as a reddish photon, we don’t notice it. The object just appears redder than it would be without the fluorescence.
So with all that said, here’s what those fluorescent neon colors are.
When not-visible-to-us ultraviolet wavelengths of light interact with certain surfaces, those ultraviolet photons are absorbed and subsequently emitted as photons with lower wavelengths that we can see. The net result being a surface that appears brighter than expected. In other words, the ultraviolet-colored light that we can’t see is converted into light that we can see, which makes fluorescent, neon colors appear to glow.
I was just about to say the same thing!
Having worked with printers for over 20yrs I felt I needed to chime in on this: 100% C, M, Y are the brightest colors you will get with conventional printing (offset, web or digital). Anything such as the 0,0,0,0 that was previously mentioned or Florescent/Neon colors have to be treated as PMS colors and there for can be much brighter based on the PMS choosen.
So… 
pardon my ignorance… but despite the dangers of having my mind blown even more, I got a few follow up questions.
Do I understand you correctly that the outermost electron shell, the valence level, is different in CMYK ink compared to spot ink? Is this valence level altered during the coating process to make prints more shiny, or is there simply another electron shell put on top of the original color electron shell? In regards to fluorescent electron shells, could they theoretically be applied to any color, e.g. could there be a neon brown?
Feels like I’m falling through a rabbit hole! 
Let’s hope not
You only really get fluorescent colours with primary and secondary colours, blue, red, green, yellow and purple.
Americans may be more familiar with day glo, which was the first adventure into fluorescent and used in World War II etc. It was an experiment in mixing fluorscent with other materials and this produced the first.
CMY is an additive process with impure inks so you can’t even fake it. But RGB is a subtractive process so digital screens are much better at displaying a neon version of a colour.