When we see a green leaf it is not a combination of yellow and blue, it is truly a green frequency of sunlight reflected by the leaf.

That’s just not true. The green of a leaf, like any colour we actually see will have a corresponding spectrum with power at a non singular location, in the case of the leaf from ‘yellowish’ to ‘blueish’. In other words, no colours exist if you define them as spectral colours like he does.

Spectral colours are clearly not what anyone should mean when they use the word colour. Those who do are silly people who really mean ‘ideal monochromatic light source’.

those that are made up of pure light and exist in a greater reality outside of our own minds.

… so he is a platonic idealist basically.