While you can edit GDA files with the DAO Toolset or pyGFF, if you have either installed, I highly recommend downloading GDApp for all your GDA-editing needs.
I highly recommend downloading and endorsing it. Examining that mod pointed me in the right direction to locate some files and enabled the writing of parts of this tutorial.
This tutorial explains: 1) how DA2 determines what headmorphs are assigned to your family after character creation 2) how you can tweak this system to integrate modded skin tints and presets into the character creator without bizarre results and 3) how to edit an existing save game to fix inappropriately-assigned headmorphs.Ī shoutout must be given to Natural Skin for being a generally excellent mod for extra (especially darker) skin tints, as well as the only mod I know of that actually adds additional family headmorph presets rather than just giving up and replacing them wholesale.