This is a case of the black plate in the printing press being under-inked. With comics multiple pages, for example 16, were printed on each side of a large sheet which was then folded, trimmed, and bound into a booklet. So a printing error on one side of the big sheet would show up on some pages of the printed comic but not others. It's interesting to see how the color looked without linework to hold it...but I find it disappointing because so many of the blackless pages contain nice Matt Baker art.
[Edited to re-insert a missing phrase]
Link to the book:
Teen-Age Romances 35