The author concludes that people whose languages have fewer words for colors than does English must be less able to perceive different colors than are English-speakers. Why would this be the case? Because different languages have different numbers of words for colours. And in another situation where languages have different numbers of words—regarding kinship relationships—speakers of languages with more words pay more attention to the details of those relationships.

Fundamentally, the author is making a phenomenon-hypothesis argument: that the observed phenomenon of languages having different numbers of color words can be explained by the hypothesis that speakers of those languages are differently-able to distinguish colors. However, the argument's structure is complicated a little by the type of support the author uses. As evidence for this hypothesis, the author relies on an analogy between color words and kinship words, saying that because having more kinship words is attributable to a better perception of kinship, having more color words must also be attributable to a better perception of colors.

Because the argument uses both phenomenon-hypothesis reasoning and reasoning by analogy, we can use weakening strategies aimed at either of these types of reasoning. This means there are more possible directions for the correct answer, so it's important to keep an open mind and not accidentally eliminate a right answer that doesn't align with our predictions.

However, we can still brainstorm weakening possibilities. To attack the argument's phenomenon-hypothesis reasoning, we could present an alternative explanation, or evidence inconsistent with the hypothesis. To attack the analogy the author uses as support, we can show that kinship and color are not analogous categories to prevent the analogy from being relevant. And no matter how the correct answer weakens, remember that it will undermine the support between the premises and the conclusion.