The colour you set is the colour that goes to the press, and the printing works takes the file as it stands.
A colour on a screen and a colour on paper are not the same thing. A screen mixes light; a press lays down ink. A document that says no more than blue leaves the answer to whichever machine prints it, and the answer changes from one machine to the next.
A document made here can say exactly what it means: the inks a press will really lay down, a brand colour ordered by name and run on a plate of its own, and a plain statement of the printing condition the file was prepared for. A printing works reads that statement and knows what it is holding.
Swatches in each of the three ways to say a colour — a grey as one number, a screen colour as three, a printing colour as four inks — each captioned with the instruction actually written into the file, and one mid-grey said three ways.
The same six colours said as bare numbers and then read through the screen profile the file carries, plus a ramp from light to dark and a sweep of measured hues: colour that still means the same thing on another screen and on a press.
Two inks the press carries on a plate of their own, each at ten strengths, a piece of work set in both, and the alignment crosses used to line the plates up — drawn in an ink every plate answers to.
Eight choices of plate among the four usual inks, each with the small program that shows it printed underneath, and two inks the press carries itself used together, every strength of one against every strength of the other.
A chart of house colours the file carries, and a drawing whose sixteen numbers are places in that chart rather than colours. The same drawing is shown twice through two charts: repainting a whole brand is one chart, not every drawing.
One pattern that states no colour of its own, laid down in five colours and in five strengths of one press ink: the fill says what colour to lay it down in. Beside them, the same hatch made of patterns that carry their own colours, which is one pattern per colour.
One drawing on three pages: a press sheet stating where the ink runs, where the blade falls and what is worth keeping, with trim marks; the same sheet cropped to the finished page; and a landscape page that states a quarter turn clockwise on an upright sheet.
One sheet larger than the finished page: the colour runs three millimetres past the blade, the trim marks stand outside it in an ink every plate carries, every colour is said in the four printing inks, and the page names the paper, the edge of the ink and the cut. Hand it the profile of a press and it claims PDF/X-4, and the sheet prints on itself which profile it is standing on.
Six colours and a grey ramp painted three times over with the very same numbers: first left to the device, then said in two ways that state the white they are measured against, the curve applied to them, and how far the base colours reach. All of that travels in a handful of numbers, with no profile to carry.
The device a file's colours were chosen for, named in plain words on the page it applies to, with a ramp and one patch per base colour painted through that device's own profile. Your printing works' description does just as well.
Four ways of writing down the rule a colour follows rather than the colours themselves: measured colours read off a table, a range cut into flat bands, one printing ink shown on a screen, and two rules joined end to end.