Change primary and secondary colors in Material UI

New Answer

With the latest version of Material UI, createMuiTheme is deprecated now. Hence, instead of that we should use createTheme

import React from 'react';
import { render } from 'react-dom';
import { MuiThemeProvider, createTheme } from '@material-ui/core/styles';
import Root from './Root';

// use default theme
// const theme = createTheme();

// Or Create your Own theme:
const theme = createTheme({
  palette: {
    secondary: {
      main: '#E33E7F'
    }
  }
});
    
function App() {
  return (
    <MuiThemeProvider theme={theme}>
      <Root />
    </MuiThemeProvider>
  );
}
    
render(<App />, document.querySelector('#app'));

Old answer

From https://material-ui.com/customization/themes/:

import React from 'react';
import { render } from 'react-dom';
import { MuiThemeProvider, createMuiTheme } from '@material-ui/core/styles';
import Root from './Root';

// use default theme
// const theme = createMuiTheme();

// Or Create your Own theme:
const theme = createMuiTheme({
  palette: {
    secondary: {
      main: '#E33E7F'
    }
  }
});
    
function App() {
  return (
    <MuiThemeProvider theme={theme}>
      <Root />
    </MuiThemeProvider>
  );
}
    
render(<App />, document.querySelector('#app'));