"Function colors" are just effect systems, which are not a new concept while also being extremely useful and super nifty. I hope someday we can stop wringing our hands in a panic over "colored functions" just because some ancient version of Javascript had a frustrating implementation of one specific effect. It reminds me of how ages ago certain people acquired an instinctual aversion to static typing attributable entirely to ancient versions of Java and its attendant verbosity and relative anemia.