Sequence can be described as follows.
* When web client sends the request , it sends payload as Blue (mentioned in question)
* In first iteration this will go to default choice , which sets payload to Red
* Via default route , flow will call itself with payload as Red
* In second iteration , as payload is Red , it will go to first route in choice router which will set payload to Blk and second iteration will end returning back payload as Blk to first iteration.
* This Blk will be again set to payload and first iteration will end returning back response as Blk