Buy him a red balloon, a new red hot wheels car, a red winter hat. These are just examples but you get the idea. One of the main things every parent has to learn when they have an Autistic child is how to make them understand what you are trying to say. It isn't that these kids are not listening. It's that they just don't understand what you're saying.
Autism is a Neurodevelopmental disorder .
The best way I have ever heard anyone explain it is that there are neurons in your brain and in order for you to process a thought, these neurons have to fire in the correct order. For instance, I can ask Alex to get me the red book. But he may instead bring me the first BOOK he sees or the first RED thing he sees. THAT'S what is happeneing. Don't give complex commands.