Oh my sweet child, I really don’t recommend this… 
First you’ll have to make the reader choose their skin color in a separate choice and gain it.
The coding would go like this:
if (neutral00){
@overlay HAND NEUTRAL 00 create
@overlay HAND NEUTRAL 00 opacity 1 in 0
}elif (neutral01){
@overlay HAND NEUTRAL 01 create
@overlay HAND NEUTRAL 01 opacity 1 in 0
}…
…
And so on for every skin tone (about 60 I think).
OR you limit it to light, medium and dark. It won’t be as acurate but it’ll spare you some nerves, time and skript lines lol. Many authors choose this option over then first 