Grey on televisions, computer displays and telephones is usually created using the RGB color model. Red, green, and blue light combined at full intensity on the black screen makes white; by lowering the intensity, it is possible to create different shades of grey. In printing, grey is usually obtained with the CMYK color model, using cyan, magenta, yellow and black. Grey is produced either by using black and white, or by combining equal amounts of cyan, magenta and yellow. Most greys have a cool or warm cast to them, as the human eye can detect even a minute amount of color
CMYK color model and ink in use. Processes called under color removal, under color addition, and gray component replacement are used to decide on the final mix; different CMYK recipes will be used depending on the printing task. CMYK or process color printing is contrasted with spot color printing, in which specific colored inks are used to generate the colors appearing on paper. Some printing presses are capable of printing with both four-color process inks and additional spot color inks at the same time. High-quality printed materials, such as marketing brochures and books, often include photographs requiring process-color printing, other graphic effects requiring