CMYK is the color space (C)Cyan/(M)Mangenta/(Y)Yellow/(K)Black, for printed media where light are reflected on a surfaces (paper) that is used for 4 colours printing process.RGB (R)Red/(G)Green/(B)Blue is the colour space for digital screens where the screen are emitting light, where the white colour are added in the colour space RGBPrinting an image that’s saved in a larger color space than the printer can handle can lead to dull-looking images as the printer is out of gamut (meaning the colors aren’t able to be reproduced on the printer).We recommend that you save or work with your file in Adobe RGB colour space before uploading your image.  When you save your file in RGB our printer software will translate the information in to CYMK colour format.