"What color is your function?" is a wonderful title. It's so good, the title alone could win the Sundance Festival.
But that post is about a JavaScript-specific limitation (not applicable to other languages), and some wishful bikeshedding about syntax (which turns out to be a leaky abstraction that makes locking ambiguous, very problematic in low-level languages).
But *color* is so catchy. It's not well defined that post, but you can't have "color" in your async, whatever that is. Just can't.