code: public final void addHelperTextColor(@ColorInt final int color) {
          if (!helperTextColors.contains(color)) {
              helperTextColors.add(color);
              verifyPasswordStrength();
          }
      }
docs: Adds a new helper text color, which should be used to highlight the helper text, which
  indicates the password strength.
  
  @param color
  The color, which should be added, as an {@link Integer} value