Trip to Hongkong during Shenzhen Layover

German passport holder can do that without any problem because she/he is not a subject of 24 hour visa free transit at all because German citizens can enter, stay and explore China for up to 30 days absolutely visa free. Also, a German passport holder can exit mainland China, Shenzhen included, to Hong Kong and return back without any limitations. However, a Colombian citizens cannot do that. Unfortunately, current rules are preventing a Colombian citizen to exit mainland China and again to enter it based on 24 hour visa free transit in the way as you have suggested. A Colombian citizen will obtain a temporary entry permit upon landing in Shenzhen at 24/144 hour visa free transit counter that will allow her/him to exit the airport, but not to exit and return back to mainland China. A Colombian citizen has to remain within Shenzhen area during her/his layover.