Print your letterhead twice, a year apart, and lay the two sheets side by side. In a surprising number of businesses the blues do not match. Not dramatically; one is a shade warmer, or flatter, or darker. Each batch looked fine on its own. Together they announce that nobody is quite in charge of the brand, which is a strange message for the most formal paperwork a company sends.
This drift is not carelessness by any one printer. It is what happens by default when colour is specified loosely and jobs move between firms, presses and years. It is also entirely preventable.
Most everyday print builds colour from four inks, cyan, magenta, yellow and black, in percentages. The same percentages do not produce identical colour everywhere: presses are calibrated differently, coated and uncoated papers hold ink differently, and digital and litho machines have different characters. Give the same CMYK recipe to three suppliers and you will get three siblings, not three twins. Add a designer who once nudged the values and a business card ordered in a hurry from a fourth website, and the drift compounds.
The established fix is to define your main brand colour as a Pantone reference, a numbered colour from a standard book that printers everywhere can either mix as an actual ink or match against a physical swatch. For letterheads, business cards and folders printed by a commercial printer, a spot-colour ink means each batch matches the book, not the memory of the last run. Where a job must print in CMYK anyway, the Pantone book still earns its keep, because it gives everyone the same target to match by eye rather than a number to reproduce blind.
If your brand guidelines currently contain only a hex code from the website, that is a screen colour, and it is not enough on paper. One conversation with a printer can nail down the trio you need: a Pantone reference, a CMYK recipe for coated stock and one for uncoated.
Once the references exist, the rest is discipline. Keep a one-page print spec alongside your logo files: colours, fonts, stock choices, and the sizes of each stationery item. Send it with every job, to every supplier, every time, and keep a printed sheet from each batch as the reference for the next. When you change printers, hand over the spec and a physical sample and ask them to match it before the first full run.
It also helps to stop scattering the stationery. Letterheads from one firm, cards from a website, folders from somewhere cheap found at deadline is how mismatches breed. One supplier printing the set together, on the same stock family, will produce paperwork that looks like it belongs to one company, and reordering becomes an email rather than a project.
The practical sequence is short. Dig out the last batch of each item and compare them honestly. Get the Pantone and CMYK references agreed and written down. Then pick a printer to hold the set. There are 2,868 printing companies listed on this site, and stationery with matched colour is bread-and-butter work for the commercial firms among them. Look through printers near you and ask how they would keep your colour consistent across items and reprints; the quality of that answer is the audition. When you are ready, request quotes for the full stationery set rather than one item, and keep a sheet from the first run in a drawer. That sheet is your brand's colour standard from now on.