How do I dequeue a Stylesheet, stored in an ‘Assets’ folder?

Two things you need to:

1. Hook into wp_enqueue_scripts with a priority later than the parent theme’s. The default is 10 so that’s a good assumption. If 11 doesn’t work, check the parent theme’s source to see which priority it’s hooked at.
2. Use wp_dequeue_style() to do the dequeueing.

That will look like:

function wpse_293836_dequeue_parent_styles(){
    wp_dequeue_style( 'theme-skin-color' );
}
add_action( 'wp_enqueue_scripts', 'wpse_293836_dequeue_parent_styles', 11 );

Note that you only need the handle of the script/style you want to dequeue. The path doesn’t matter. The handle should just be theme-skin-color as WordPress adds -css to the ID.