(You might also see other resource types, but in this tutorial I’m only working with the things that say SKINTONE. You’ll see something like this (which is the upper left part of the S4S window): Skintone packages don’t have the Studio tab, only the Warehouse. I am going to assume that you have some basic familiarity with Sims4Studio and not tell you how to open a package file in it. It’s possible S4S may later add prettier GUI tools for at least some of this process. (This is particularly relevant to people who have downloaded a creator’s own updated version of their custom skin colors, but have totally different ideas about where they should appear in CAS.) You can also use this method to change whether custom skin colors that already work in the game show up as Warm, Neutral, Cool, or Miscellaneous, or to change the values of the light-dark sliders on custom skin colors.

(This is particularly relevant to Macintosh users who can’t use CmarNYC’s automated tools, or to people who just want to do it themselves at least once so they have a better idea what’s under the hood.) You can use this method to update any non-default custom skin COLORS, as well as defaults that are not texture-only (but not any other type of skin-related custom content, and not texture-only defaults which already needed updating after the October patch), that do not work after the December 2020 skintone patch. EDIT : S4S has updated with a batchfix and several other related improvements so I’ll be updating this post soon to focus more on editing already-fixed files (and to update the names of the fields).

Sims 4 cc default skin colors