Your brand guide names a particular colour, while a printer’s quote says the job will run in four-colour process. Those statements can coexist, but they do not automatically promise the same physical ink on the paper.
Adobe’s explanation of spot and process colours distinguishes a premixed spot ink from colours produced using the standard cyan, magenta, yellow and black process inks. A spot colour in a design file can also be converted or simulated, depending on the output workflow.
For a small stationery project, ask whether the named colour is being printed as a separate ink or reproduced as a process approximation. Confirm the paper and finish too. A colour name on the artwork is not a substitute for an agreed production specification.
Imagine comparing two quotes for the same invitation. One may include a separate spot plate while the other assumes a process conversion. Comparing only the final price hides a difference in the product being offered.
Check the proof at the right level
A PDF can show layout and wording, but the screen does not become the final paper and ink. Ask what kind of proof is available and which decisions it can reliably support. Mark the colour-critical areas instead of requesting an undefined improvement in “vibrancy.”
Keep an editable master and a clearly named output file. If the printer requests a conversion, make it in the delivery copy according to the agreed specification. Record any approved substitution so a later reprint does not accidentally use a different process.
Check swatches and separations with the production team when there is uncertainty. A duplicate colour name or an unintended spot swatch can create confusion even if the composite preview looks plausible.
The practical question is not which method is always better. It is whether the artwork, quotation, proof and final production all describe the same job. Settling that before approval makes the finished brand material much easier to judge fairly.