Gmaps InfoWindow Style

demo.js

import React from 'react';
import {Gmaps, InfoWindow} from 'react-gmaps';

const coords = {
  lat: 51.5258541,
  lng: -0.08040660000006028
};

const App = React.createClass({

  render() {
    return (
      <div>
        <Gmaps
          width={'400px'}
          height={'300px'}
          lat={coords.lat}
          lng={coords.lng}
          zoom={12}>
          <InfoWindow
            lat={coords.lat}
            lng={coords.lng}
            content={'<div class="info-window">I\'m red</div>'} />
        </Gmaps>
      </div>
    );
  }

});

React.render(<App />, document.getElementById('gmaps'));

style.css

.info-window {
  background-color: red;
}