src/pages/about/index.styled-components.tsx

import React from 'react';
import { styled } from 'umi';
const Wrapper = styled.div`
  h1 { background: rgb(121, 184, 242); }
`;
export default function Page() {
  return (
    <Wrapper>
      <h1>Page index</h1>
    </Wrapper>
  );
}