That is truly remarkable! I've heard of people associating words with colors before, and it makes sense to me in a way.

Thinking like a speech pathologist, might colors be a way in to get him to expand his phrasing? Our way in to our son was vehicles. That's how he learned colors, shapes, spelling, even used car shaped pop beads to get his motor skills going.
If he will echo you at all, you might be able to eventually get him to say "I want red."
Then, "I want red youtube."
Then remove the red for "I want youtube."
It won't change overnight, of course. But if you can break through and get that first "I want" the others may come on easier.

I really enjoy when the speech therapists will allow me to be in the room when they work with him. I try to retain as much as I can to use at home.