This article gets referenced a lot, but it does a poor job of defining what color actually is.
The biggest issue the article describes — inability for sync code to wait for an async result — is limited mostly to JavaScript, and doesn't exist in most other languages that have async and a blocking wait (they can call red functions from blue functions).
If this architectural hurdle is meant to be the color, then lots of languages with async functions don't have it. This reduces the coloring problem down to a minor issue of whether async needs to be used with a special syntax or not, and that's not such a big deal, and some may prefer async to be explicit anyway.
Python also has it. You can call async code with `asyncio.run` but it is extremely limited by the fact that nested event loops are prohibited. Any function that uses it becomes extremely brittle because it can't be called from async functions unlike all other synchronous code.
This is for the most part an intentional design decision to "make sure that when the user is already in async code they don't call the sync form out of laziness." [1]
The biggest issue the article describes — inability for sync code to wait for an async result — is limited mostly to JavaScript, and doesn't exist in most other languages that have async and a blocking wait (they can call red functions from blue functions).
If this architectural hurdle is meant to be the color, then lots of languages with async functions don't have it. This reduces the coloring problem down to a minor issue of whether async needs to be used with a special syntax or not, and that's not such a big deal, and some may prefer async to be explicit anyway.