It will be the same for all characters - Real, styled and toons.
So, there are a number of ways of doing this:
The quickest way is to edit the colour is by messing around with the Brightness and Saturation tabs in your Characters material settings to change the skin tone from dark to light or vice versa.
Select you character and go to the Modify window and select the materials tab. Scroll down to the 4 skin textures - there is one for the face, body, arms and legs. You need to select them all to ensure that they all end up the same colour. Once you've done this click on the Base color map. When you click it, the adjust colour tab open. This is where you can make the necessary adjustments to get the skin tone you want.
OCalvin does a Youtube tutorial showing all of these steps in more detai:https://www.youtube.com/watch?v=lZMetytBnwA
Alternatively, if you want a more accurate result you could manually edit these skin diffuse maps in Photoshop or some other photo editing software. I use Sketchbook, which is free.
If that is too much work for you and you have the budget, you could purchase this CC3 Toon bundle, which included 12 charactesr with various skin colours. Depending on the shape of your character you could simply replace the skin textures with the ones from this pack....https://marketplace.reallusion.com/cc3-toon-bundle-vol--1