This is something i have noticed throughout interacting with other NPCs and i've always wondered why. Here is an example.
Here you can see that some Wood Elves have a lighter skin tone that is not available in the character creation.
This can also be seen among Bretons, Imperials, and even Altmer as shown below
I know that some NPCs can also have Hair colors not available to other races, like Black hair on an Altmer for example, but this is something i wanted to bring up and am wondering why this is the way it is?