Practical colour theory: Additive colour mixing
Do an experiment: ask someone how many primary colours there are and what they are. There's likely to be confusion, some referencing printing cartridges that have cyan, magenta and yellow to mix colours while you'll remember we said that red, green and blue are our primary colours when working with video.
This confusion is created by a lack of understanding of colour systems.
We have different ones for different things, and the way colours mix in painting and printing is in some ways exactly the opposite of how it works when you work with media displayed on screens. The printing industry uses a "deductive" colour system while we use an "additive" one.
Implementations that use deductive colour mixing use variants of the CMYK colour space (cyan, magenta, yellow and black) while we use variants of the RGB colour space. It's important to know that graphic assets could be stored in either, and it's not always possible to accurately convert between the two (because the sizes of the colour spaces don't align very well), so creating media for print is actually fundamentally different from creating media for use on screens.
When working with graphic designers, printers and other users of CMYK, make it clear that you will have to receive RGB versions of whatever they produce, and that they need to make sure that colour fidelity is maintained after conversion.
A client will typically not be happy if their corporate colours are not presented accurately in your work.