The problem here is that you are looking at a document with its own colourspace which is specifically designed to print correctly on the CreateSpace service. I suspect you will only see the colours correctly if your setup is properly calibrated and your viewer can handle colour profiles properly.
You can do some weird things with colourspace. how do the pdf examples given you the github link you provided get displayed on your screen? I have also compiled your MWE and on my screen it look black on adobe reader under linux.
Your sample shows black here and the colour picker on my environment gets RGB(0,0,0). I definitely thing your environment doesn't handle the colourspace properly. As a matter of fact I have tried it on a Mac and get what you described when using Adobe Reader but using Preview I get RGB(0,0,0). This is definitely a colourspace interpretation issue. Your sceen has its own response, the system will try and match this by translating the colourspace of the document (usually RGB) to what the screen can handle. For printing it is the same: the printer will have its own response.
When doing photography, one can spend a fair amount of time calibrating screen/printer/scanner... and photography software will be able to switch from one profile to another to show the user exactly how it will show and the different output devices. Most professional printing company will give you their own printer profile (as the ones provided by the CreateSpace package). Now how to get Adobe Reader to do the translation properly... I have no idea. I guess it will use the system profile and hand the translation to the OS requiring the user to calibrate the system properly.