如何处理在defaultProps中有值的可选属性？

import React from 'react';

class Button extends React.Component {
  render() {
    const { color, children } = this.props;
    return (
      <button style={{ backgroundColor: color }}>
        {children}
      </button>
    );
  }
}

Button.defaultProps = {
  color: 'blue'
};

export default Button;

import React from 'react';
import PropTypes from 'prop-types';

class Button extends React.Component {
  render() {
    const { color, children } = this.props;
    return (
      <button style={{ backgroundColor: color }}>
        {children}
      </button>
    );
  }
}

Button.defaultProps = {
  color: 'blue'
};

Button.propTypes = {
  color: PropTypes.string,
  children: PropTypes.node.isRequired
};

export default Button;