如何更改Material-UI的卡片表头正面？

import React from 'react';
import { Card, CardHeader } from '@material-ui/core';
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
  header: {
    background: 'linear-gradient(to right, #ff9800, #f44336)',
    color: '#fff',
  },
});

const MyCard = () => {
  const classes = useStyles();

  return (
    <Card>
      <CardHeader
        title="Card Title"
        subheader="Card Subheader"
        className={classes.header}
      />
      {/* Card Content */}
    </Card>
  );
};