Snackbar should be added in a view which contains a CoordinatorLayout.

SnackBarExample.java

Snackbar snackbar = Snackbar
        .make(view, R.string.error_occured, Snackbar.LENGTH_LONG)
        .setAction(R.string.retry, new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(AlertsActivity.this, getString(R.string.retry_message), Toast.LENGTH_LONG).show();
            }
        });
snackbar.setActionTextColor(Color.RED);
View snackbarView = snackbar.getView();
snackbarView.setBackgroundColor(ContextCompat.getColor(this, R.color.colorAccent));
TextView textView = snackbarView.findViewById(com.google.android.material.R.id.snackbar_text);
textView.setTextColor(Color.GREEN);
snackbar.show();