there is always some yellow for me

I wonder how they came up with this chart, and what the underlying principles are.‌ For example, if we take the vertical axis as the primary emotion, and the horizontal axis as the secondary emotion...

disgust + joy = ironic
joy + disgust = disdain

but...
fear + joy = protective
joy + fear = excitement

The first pair seems similar enough, but the second pair is not something I've considered similar.