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!

The problem.

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’.