If your journey started in a European Union (EU) country and you have nothing to declare, use the blue exit. If you have goods to declare, go to the red Customs point.
If your journey began in a country outside the European Union, go to the red Customs point if you have goods to declare or use the green exit if you don't.
If your baggage is checked through to your final destination, that’s where you clear customs. If you’re collecting your baggage and checking in to your next flight yourself, you need to pass through customs at Heathrow.
You’re responsible for the goods you carry through, so make sure what you take into the UK belongs to you.