CMYK is an acronym for Cyan, Magenta, Yellow and Black: it is a four-color model that we use in our prints. We will print your order with a mixture of percentages of these four colours : it means you can prepare the graphics using all the colors of the CMYK spectrum.
As indicated in the instruction file, create your own graphics using this color model to avoid color variations.
If you don't use a graphics program you may not be able to choose the correct color method: so we will automatically convert your file with a separating profile your graphics to CMYK.
Also, we offer Color Guides printed on various materials to help you creating your colours: please note that each colour appears in a different way watching a monitor or watching it printed.
If you still have any doubts, please contact us. We'll be happy to help !