Re: PMAG 7.62 in FDE or OD...
1st, they are NOT for AR-10s (AR-10 = Armalite)...the 7.62 PMAGs are for DPMS LR-308, KAC SR-25, POF P-308, etc. pattern rifles.
2nd, like good ol' Henry Ford said...you can get them in any color you like as long as its black! Magpul has stated several times that they have no plans to introduce different colors for the 7.62 PMAGs despite people asking for them. Will they change their mind on this at some point...maybe, but not in the foreseeable future. If you want different colors...Krylon Fusion/Camo Fusion is your friend (available in a variety of colors, but they do have OD and a couple different sand/dirt colors).