Yes, we are not strictly proposing function coloring. I believe the other way where we make Suspend and implicit requirement with context functions can potentially be used to automatically CPS transform functions that carry that requirement. This approach would be similar to the ergonomics of LOOM, where you get non-blocking CPS underneath through the VirtualThread or the previous Continuation interface.
The map(_.bind) case in our examples already works non-blocking with our implementation based on LOOM, Context functions with requirements seem to work with map. We could potentially piggyback on LOOM for the JVM if we figure out a way to have a different runtime in native and js.
Another alternative is to create a LOOM style runtime for just the continuation disregarding virtual threads and things we leave abstract to ExecutionContext but that is more or less the impl of what we proposed above.