Computer monitors are given a range of Red, Cyan, and Green to compose all the colours that we see. While it's not the primary colours we learn in elementary school, these are the colours our eyes work with.
Understanding that, the following article uses the concept of an afterimage to show you a colour that isn't in your monitor.
I'd almost wonder if someone has made the colour you're about to see in the image here. Just follow the instructions, and the brilliant colour comes easily.
See if you can capture the colour from the image's effects.
Make a colour based on what you see, and post it here.
Share what you see.