RGB versus CMYK
Computer monitors emit color as RGB (red, green, blue) light. Although all colors of the visible spectrum can be produced by merging red, green and blue light, monitors are capable of displaying only a limited gamut (i.e., range) of the visible spectrum.
Whereas monitors emit light, inked paper absorbs or reflects specific wavelengths. Cyan, magenta and yellow pigments serve as filters, subtracting varying degrees of red, green and blue from white light to produce a selective gamut of spectral colors. Like monitors, printing inks also produce a color gamut that is only a subset of the visible spectrum, although the range is not the same for both. Consequently, the same art displayed on a computer monitor may not match to that printed in a publication. Also, because printing processes such as offset lithography use CMYK (cyan, magenta, yellow, black) inks, digital art must be converted to CMYK color for print. Some printers prefer digital art files be supplied in the RGB color space with ICC profiles attached. Images can then be converted to the CMYK color space by the printer using color management methods that honor profiles if present; this helps preserve the best possible detail and vibrancy.
Visible color spectrum with print gamut
It can sometimes be difficult to visualize the reason for color shift in color space conversion. The best way to see the color differences between the CMYK and RGB color spaces is to look at a color gamut comparison chart. Some printers may prefer your files be delivered in RGB with ICC profiles attached, as this allows the printer to use color management methods when converting to CMYK. Other printers may prefer your files in the CMYK (Cyan/Magenta/Yellow/Black) mode, as this is the mode required for the printing process. If an RGB (Red/Green/Blue) file is submitted, it must be converted to CMYK for print.
Digital art that is comprised of spot colors (e.g., special colors: any colors that are not CMYK process colors), generally require conversion to the CMYK color space to enable file use. Because color gamut’s for spot color libraries, such as those associated with the Pantone Matching System (PMS), usually extend beyond the ranges of the CMYK color gamut, some spot colors may not be represented effectively using CMYK process inks.
Pantone colours are an agreed, industry standard set of colours that can be matched to accurately over a variety of processes, equipment and materials. They are identified as a series of numbers instead of names (except with fashion colours), so you will hear the reference PANTONE 2985 C instead of Sky Blue. This helps a great deal as one person’s idea of what Sky Blue is may be very different to another person, but with a number you can refer to the chart and you know exactly what you are getting. Keeping colours consistent is a big issue with Infiniti Mixed Media and is very difficult to do over different systems like print and the web.