Everyone is both right and wrong
the official standard for those 80pin cables is for the cable to made as Cable select cables, as such the end connector must be master
now, in realiaity, most makers do not follow the standard, but some do. in most cases you can get away hooking it up anyway you please, but in your case you have a cable that confrms to standrd by being cable select ( having a line knocked out between master and slave )
If you wanna play it safe and get it right all the time, the Black goes to master, grey goes to slave and blue goes to host