Assuming that you want to change all the ones you have circled red then you would do something like this. https://gist.github.com/MrOtherGuy/8816d7b388200119279da6f735539acb
Here I'm just linking them to use some other built-in icons with the exception of those that you have not circled, for those you need to set them use their original icon. It wouldn't need to be this complicated if you didn't want that "generic" folder icon to change.