When Scout/Koala or even better, Grunt , is running, it will detect changes from the /sass folder and will compile the .css in the theme/styles/css folder. These could be loaded in your index.html.
"$", for example "$color-text-default"
Probably nothing changes, because Koala isn't running correctly? I have to look into this before I could give you an answer.
PS. For more details on SASS, please read this blogpost.