Platform API figures what operating system you are on. 

backgroundColor: Platform.OS === "android" ? Colors.primary : "white"

backgroundColor: Platform.OS === "ios" ? Colors.primary : "white"

Alternate is to use Platform.select

<View
style={{
       ...styles.headerBase
       ...Platform.select({
       ios: styles.headerIOS,
       android: styles.headerAndroid
      })
      }}> 
</View>