To simply state that the document needs to be set up in CMYK color mode is not necessarily the proper solution. It is possible though, that setting up the document in CMYK color mode will fix the problem but it is more likely that there are several issues.
You mentioned "printing press". The very first thing you need to know before creating your document for printing is... What will the actual printing process be? Will the printers be using CMYK (four color process) inks or will they be using CMYK combined with extra spot colors? Will they be printing spot colors only? If the printing company will be using CMYK ink, then absolutely yes, create your document in CMYK color mode. However, if the printing company will be using spot colors only, RGB color mode would be appropriate for your document. In that case you would color your artwork with the specific spot colors and you could probably use spot colors directly from Pantone color books.
After asking your printer what printing process they are going to use and assuming it is going to be CMYK, the next thing you would benefit from doing would be asking them the exact name of the inks and brand and company. This is actually very important because most ink companies offer downloadable color profiles for their ink sets that can be loaded into Illustrator, Photoshop, and Corel in each program's color settings preferences. Now any artwork created will be using the actual color values of the printing inks.
When saving your artwork file to be sent to the printer, be sure to embed the color profile of your document. It will also be important to include that color profile file that you downloaded from the ink manufacturers website. Next you would request that the printing company load and use that color profile file into their software when opening your document.
That process is not 100% foolproof because chances are your monitor and their computer monitor will not be color calibrated the exact same way but at least both you and the printer will be more in sync together as far as what you created vs. the final printed product.