I just edited my character's skin and thought I should share this with others...
After opening your Sword or Shield save file
1) Click on the SAV tab
2) Select Block Data
3) Under the Block Key dropdown, select *Object MyStatus
4) Put the values of the skin tone you want that match your character's gender under Skin and MomSkin below
Male:
Skin: 15750773674524975186
MomSkin: 16295240065100649920
Skin: 15750772575013346975
MomSkin: 16295241164612278131
Skin: 15750771475501718764
MomSkin: 16295242264123906342
Skin: 15750770375990090553
MomSkin: 16295243363635534553
Female:
Skin: 15683315162178948477
MomSkin: 66653365124950412
Skin: 15683311863644063844
MomSkin: 66654464636578623
Skin: 15683312963155692055
MomSkin: 66655564148206834
Skin: 15683309664620807422
MomSkin: 66656663659835045
NOTICE: If you changed a female player's skin tone, you will end up with a bugged (unchangeable) starting model of that character! To fix this, simply go to a Salon (earliest is in Motostoke) and pay 1000 for a makeup change, select the lipstick tab and make ANY selection then confirm!
Here's an example:
There are no problems if you're changing a male player's skin tone, so you don't have to worry about this.