Have you ever seen a blue on screen that just didn’t print like you thought it would? Be very careful when creating blues for print. The range of colors that can be reproduced in CMYK mode is considerably smaller than the RGB range of colors reproducible on a standard monitor, so when the file it rendered to CMYK for printing, the colors may shift and lose vividness.
Printing presses, desktop printers and monitors produce colors in different ways. Screens and presses are NOT made to match each other, even if they sometimes do. Monitors use the RGB (red, green, blue) color model, which usually supports a wider spectrum of colors. Printers use the CMYK (cyan, magenta, yellow, black) color model, which can reproduce most—but not all—of the colors in the RGB color model.