How to change the theme skin?

[sandeshkatakam]

I have noticed that there is an option to change the theme skin in the _config.yml in the minimal mistakes theme.
I have tried to add these line as mentioned in the minimal mistakes theme guide at the beginning of _config.yml file :
theme: minimal-mistakes-jekyll
minimal_mistakes_skin: "dark" # "air", "aqua", "contrast", "dark", "dirt", "neon", "mint", "plum", "sunrise"

But there was no change in the theme skin color.
Please suggest me how to fix this issue.

[mvhirsch]

You probably won't find it here. minimal-mistakes theme (v4.11.1) support after this project was forked.