ELI5 Primary Colors - are they red green blue or red yellow blue?

Why are red, blue, and green considered primary colors for our TVs and Computer Screens, but for our printer ink, we have cyan, magenta, and yellow are primary colors in ink? What about red yellow blue as we are taught as 5 year olds? Could there be a fourth primary color? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: jefferey1313, themuffinman91, amoebachant, goldgibbon, dodweon, try-catch-finally and kile147 To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]