title: Mui - remix with typescript - Set primary color in theme via .env
body: <p>Since remix.run renders serverside, I expect it would be possible to set colors via .env file. But in the <a href="https://github.com/mui/material-ui/blob/master/examples/remix-with-typescript/app/entry.client.tsx" rel="nofollow noreferrer">entry.client.tsx</a> the theme is imported and set in the ThemeProvider. When the color palette uses .env variables it breaks in the browser, because process is not defined.</p>
  <pre><code>const theme = createTheme({
    palette: {
      mode: 'light',
      primary: {
        main: process.env.PRIMARY_COLOR,
      },
    }
  });
  </code></pre>
  <p>Any ideas how to use .env to create a theme?</p>