COLOUR THEORY. RGB or CMYK
As an artist I think about colour using an established colour model. The primary colours are Blue Red Yellow, [BRY]. With these three colours I can, in theory, mix any other colour. The secondary colours if you mix two primaries are Purple, Orange, and Green. Simple and well proven!
My problem is that many years ago, when I started looking around inside my first computer, I was puzzled. There seemed to be two conflicting sorts of colour language in Adobe PhotoShop software. There was ‘CMYK’ and ‘RGB’.