Final answer:
Skin color changes to yellow, grey, or sallow can be due to physiological factors such as liver diseases leading to jaundice, reduced skin elasticity and collagen with aging, or cyanosis from decreased oxygenation. Diseases like Addison's disease can also cause skin darkening.
Step-by-step explanation:
Environmental factors can affect our skin in various ways, but when it comes to skin turning yellow, grey, or sallow, we must look at physiological causes rather than external environmental factors. Liver diseases such as liver cancer can lead to the accumulation of bile and bilirubin, causing the skin to appear yellow, known as jaundice. Grey or sallow skin can occur due to a variety of reasons including aging, which reduces the production of collagen and elastin, leading to paler skin tones. Additionally, a lack of oxygenation can make the skin turn ashen or even blue, a condition known as cyanosis. Moreover, certain diseases like Addison's disease can cause the skin to darken due to an increase in adrenocorticotropic hormone (ACTH).