[captainmuon]

I don't know, I've always thought green threads refers to the coding style of Go or Java's Project Loom - you write code that looks like multithreading and call blocking methods like `socket.receive()`. And then deep down in each IO call, there is some magic that suspends the green thread, and resumes it when data is available.

I think the colored function thing is often thoroughly misunderstood. There is a real difference between a function that returns `string` vs. `Future<string>`. It's not arbitrary but just a matter of typing. Languages could have more syntactic sugar to bridge both worlds of course. And you can get rid of the distinction as goroutines etc. show.

But actually I wonder if it would be useful to keep some colors. Maybe you could have an effect system and mark functions as "computationally expensive" / "blocking" vs. "computationally trivial". The compiler would prevent you from calling the blocking functions from the GUI thread, but you could `async` or `go` them to another thread and resume when finished.