Ninefold PrintYou approve a logo on screen, it prints correctly on the business cards, and then the same logo on the folder is slightly off. Nobody did anything wrong, and the two pieces genuinely do not match.
Color reproduction depends on how the ink is made, what it is printed on and which process laid it down. Change any of those and the result moves.
Spot color and process color are not the same thing
Spot color is ink mixed to a formula before it goes on the press, the way paint is mixed at a hardware store. A Pantone number specifies that recipe. Every sheet gets the identical ink, so the color is consistent by construction.
Process color builds the appearance from four inks: cyan, magenta, yellow and black, laid down as tiny dots that your eye combines. It can produce an enormous range, but it is a simulation. Some colors, particularly bright oranges, deep blues and anything approaching a metallic, sit outside what four process inks can reach.
If your brand color is specified as a Pantone and reproduced in process, it will be close and not exact. That is not a printing error. It is the difference between mixing a color and approximating it.
Coated and uncoated shift the same ink
The identical spot ink prints differently on coated and uncoated stock. On coated, it sits on the surface and stays saturated. On uncoated, it soaks into the fiber and reads softer and darker.
This is why Pantone publishes separate coated and uncoated values, written as a C or U suffix. 185 C and 185 U are the same ink on different paper, and they do not look the same. A brand guideline that names only one of them is under-specified for print.
If a brand runs across coated collateral and uncoated stationery, expect a visible difference and decide up front which one is the reference.
Digital and offset reach color differently
Offset can carry a real spot ink on its own plate. Digital normally cannot, and simulates it from process. For most colors the simulation is good; for a saturated brand color it can be the difference somebody notices when two pieces are side by side.
This matters when a job splits across processes: a short run digitally and a longer run offset, printed months apart, from the same file. See digital or offset for why a job ends up on one or the other.
Substrate changes everything again
A brand color on coroplast or vinyl is a different problem altogether. Large format uses different inks on materials that absorb and reflect differently, and a sign is usually viewed outdoors in daylight next to nothing else.
The good news is that a sign is rarely held next to a business card. Exact matching matters most where two pieces are seen together.
What to do about it
Decide what the reference is. One printed piece, held in the hand, that everything else is matched to. A screen is not a reference; monitors are backlit and printing is not.
Specify coated and uncoated values. If your guidelines only give one, get both defined, ideally by printing them.
Say when it is critical. "This has to match the existing packaging" changes how a job is set up, what proof you should ask for, and sometimes which shop it goes to. Say it in the brief rather than at the proof.
Ask for the right proof. A PDF on a screen tells you nothing about color. A printed proof on the actual stock tells you a great deal. A press check tells you most, and costs most.
Accept a tolerance. Commercial printing has variation within a run and between runs. Perfect identity across processes and substrates is not achievable, and a shop that promises it is describing an aspiration.
The part worth paying attention to
Most brand color problems are not caused at the press. They are caused by a specification that named a Pantone and nothing else, and then ran across three processes and four substrates without anyone deciding what the reference was.
That decision is cheap to make once and expensive to make repeatedly. If holding it consistent across pieces printed in different places is the problem, that is precisely the thing to hand over.