The important insight was that dark orange/brown only exists in a context. There has to be something lighter visible for it to be perceived as dark. Whereas pin

The important insight was that dark orange/brown only exists in a context. There has to be something lighter visible for it to be perceived as dark. Whereas pink is a different mix of light than red. You can't make a red light bulb pink no matter how bright you make it. And you can't make an orange light bulb brown without putting a different brighter light alongside it.