code: @NonNull
    @SuppressWarnings("WeakerAccess")
    public SnackbarWrapper appendMessage(@NonNull CharSequence message, @ColorInt int color) {
      Spannable spannable = new SpannableString(message);
      spannable.setSpan(new ForegroundColorSpan(color), 0, spannable.length(),
          Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
      messageView.append(spannable);
      return this;
    }
docs: Append text in the specified color to the Snackbar.
  
  @param message The text to append.
  @param color   The color to apply to the text.
  @return This instance.