The siamese cat has darker pigmentation, due to some proteins functioning differently at lower temperature, because the extremities which are dark have a lower temperature. They are farther from the warmer body core and have long, thin shapes which readily lose heat/have a lower temperature.
Work Step by Step
The key is to use the hint about body temperature and why the darker parts of the body would be cooler/end up darker. Think about walking on a cool day-- what gets cold first, hands, nose, and feet or body core?