>>4449975
>I don't know what's this for
It's because the distribution and visibility of blood is not even throughout the body. There are places with more or fewer blood vessels, and places where the skin/fat obscures those vessels more or less. This creates places where the skin is more pink or less pink (the cheeks, fingertips, breasts, etc) . There are also places where the skin tends to be more blue/cool and places where it tends to be more yellow.