No this is impossible. First of all css files does not understand anything else than css. So PHP or HTML isn't allowed there. And the other reason is that the scss file is compiled and this is done once. So all users will be served the exact same file.
What you probably can do is add a class="{{ $conditionToDebug ? 'debug_mode' : '' }}" to your tag. Now you can make css rules like this:
.debug_mode .block_container {
background-color: yellow;
}
// or more scss like
.block_container {
.debug_mode & {
background-color: yellow;
}
}
or another option is to make a separat debug.css file and only include that file in the head if you want that to happen Eg, based on a request parameter, debug mode, etc.