The 1 Bozo the Clown issue of Four Color (Dell, 1942 series) (#285) is considered by Dell to be the first issue of this series.
Full indicia's (capitalization original):
2: BOZO THE CLOWN and the WEATHER WIZARD
3: BOZO THE CLOWN and THE MYSTERIOUS BOX OF SHADOWS
Indicia and tracking information from Jon Ingersoll via the GCD Error List (October 10, 2009).