The Free On-line Dictionary of Computing (30 December 2018):

four-colour glossies

   1. Literature created by marketroids that allegedly contains
   technical specs but which is in fact as superficial as
   possible without being totally content-free.  "Forget the
   four-colour glossies, give me the tech ref manuals."  Often
   applied as an indication of superficiality even when the
   material is printed on ordinary paper in black and white.
   Four-colour-glossy manuals are *never* useful for finding a
   problem.

   2. [rare] Applied by extension to manual pages that don't
   contain enough information to diagnose why the program doesn't
   produce the expected or desired output.