The sources mentioned aren't all poets, but I wondered something like this too. Those ancient texts were preserved because they were extraordinary. That does have potential for issues when it comes to drawing broader inferences from them.

However, it's an ancillary concern. As I understand it, the essay's focus is on how those ancient writers placed several qualities under the label of "colour" so, if we want to interpret those properly—irrespective of whether they're representative of the wider Greek populace—we need to be aware of that and not limit our thinking when we encounter "chroa/chroiá" solely to our modern use of the label, so nothing (or, at least, less) is lost in translation.