Final answer:
The author refers to colors when mentioning 'shades of green and brown,' pointing out how different languages can affect color perception and categorization.
Step-by-step explanation:
When the author mentions 'shades of green and brown,' they are referring to colors. This is understood in the context of color perception and the influence of language on how we recognize and categorize colors. The referenced research by Paul Kay and Willet Kempton, as well as the work of Berlin and Kay, show that the language we speak can affect our distinguishing of colors, with languages that have distinct words for different colors resulting in a clearer categorical boundary between those colors, such as blue and green. Cultures that have fewer color terms may not differentiate colors in the same way as cultures with more color terms, but still, have the capacity to perceive various colors.