The cones in the human eye are color sensitive to the primary colors of red, green and blue light. The combination of which is: white. Collectively, the eye/brain can distinguish millions of different colors.  A digital camera's sensor array has millions of individual pixel's that have a red, green and blue transparent filters to capture your subjects multiples of primary and secondary colors. So you view your image on your cameras preview screen and the colors are there. Now, you upload to your computer, and you preview it, your color monitor presents it in an accurate color display. Now, you want to print it, but wait a minute, my printer doesn't have primary color cartridges, it has cartridges of secondary colors; Cyan (bluish-green), Magenta (bluish-red) and Yellow. Yes, most basic ink-jet printers today provide very good and sometimes excellent rendition of your captured colors with individual color cartridges of  Black, Magenta, Cyan and Yellow. How does your printer do that? The answer is, subtractive and additive color mixing of these four colors via your ink jet printer. And your color image is printed on: white photo paper. Amazing stuff isn't it?