title: Problem in change background color in createStackNavigator..?
body: <p>I am new in react native. I want to change background color in tabLayout. Me code is here:</p>
  
  <p><strong>MainTabNavigator.js</strong></p>
  
  <pre><code>import React from 'react';
  import { Platform } from 'react-native';
  import { createStackNavigator, createBottomTabNavigator } from 'react-navigation';
  
  import TabBarIcon from '../components/TabBarIcon';
  import HomeScreen from '../screens/HomeScreen';
  import LinksScreen from '../screens/LinksScreen';
  import SettingsScreen from '../screens/SettingsScreen';
  
  const HomeStack = createStackNavigator({
    Home: HomeScreen,
  });
  
  HomeStack.navigationOptions = {
    tabBarLabel: 'Offer',
    tabBarIcon: ({ focused }) =&gt; (
      &lt;TabBarIcon
        focused={focused}
        name={
          Platform.OS === 'ios'
            ? `ios-information-circle${focused ? '' : '-outline'}`
            : 'md-information-circle'
        }
      /&gt;
    ),
  };
  
  const LinksStack = createStackNavigator({
    Links: LinksScreen,
  });
  
  LinksStack.navigationOptions = {
    tabBarLabel: 'Categories',
    tabBarIcon: ({ focused }) =&gt; (
      &lt;TabBarIcon
        focused={focused}
        name={Platform.OS === 'ios' ? `ios-link${focused ? '' : '-outline'}` : 'md-link'}
      /&gt;
    )
  };
  
  const SettingsStack = createStackNavigator({
    Settings: SettingsScreen,
  });
  
  SettingsStack.navigationOptions = {
    tabBarLabel: 'Settings',
    tabBarIcon: ({ focused }) =&gt; (
      &lt;TabBarIcon
        focused={focused}
        name={Platform.OS === 'ios' ? `ios-options${focused ? '' : '-outline'}` : 'md-options'}
      /&gt;
    )
  };
  
  export default createBottomTabNavigator({
  
    LinksStack,
     HomeStack,
    SettingsStack,
  });
  </code></pre>
  
  <p>I don't know where i should change in my code.</p>