/*In the ts file:*/
this.snackBar.openFromComponent(SnackComponent, {
      data: {
        message: 'Hello, snackbar!'
      },
      duration: 2000,
      panelClass: ['snackbar'] /*This is the class you'll refer to*/
    });
/*In the css file:*/
.snackbar {
  background: lightgreen;
}