Three Story Volumes with Color Paper Covers

Perhaps these were produced as an experimental cost-saving measure for promotional volumes. The covers use the colored paper of the promotional two story books. The cost of using the colored paper was probably cheaper than running the covers with two ink colors. The titles in these two volumes were used promotionally for many years. The red covered book was dated June 1972 by a previous owner.

Known editions
(June 1972) red cover
The Case of the Careless Cupid by Erle Stanley Gardner 
A Fine And Private Place by Ellery Queen
The Kidnaped Child by John Creasey as Gordon Ashe

(green cover)
The Case of the Fabulous Fake by Erle Stanley Gardner 
El Rancho Rio by Mignon G. Eberhart
The Underground Man by Ross MacDonald