USMC "Reversable"? cammo.

I'm doing a Dio on the 2nd Division on Tarawa and the Cammo Fatigues comes in 2 types -

1 - Light Khaki base with light and dark brown blotches over it

2- Darker Tan base with light and dark brown blotches, and OD green blotches added.

I've researched both patterns and found that the USMC called them reversable.  To me, reversable means something like the SS Autumn pattern on one side, White on the other for winter operations.

Question: Anyone know what each pattern was supposed to be for?(i.e - use this side when here....this side when there).

Just a question and a thought.  Thanks Guys and Gals.