As someone who works in the industry, I can guess that speaking about guns in general, FDE guns right now are probably outselling OD at a ratio of about 10:1. The being said, the FDE seems to be slowing down and OD is picking up, a little. With all the coatings and new anodizing technology coming out there are going to be so many choices for colors it will be hard to say what is the hot thing next.
It's your gun , you can have sky blue with rainbow accents if you want.
That said , Nickle used to be the cool handgun finish for about 100yrs .Long guns were blued and walnut until 1960s , and hardwood stained to look quasi-walnut for another 25. The black on black has become *normal* within past 20yrs.
There has been periodic minor intrest in OD green ever since WWII green parkerization., and probably will continue to minor intrest indefinatly.
I'm predicting that FDE will become as dated as tailfins.
So the reason FDE and OD are becoming popular is that black is not a color that occurs in nature. This causes black to stand out A LOT when in contrast with a green wooded or jungle environment and a tannish desert or dry grassland environment. Why would you want your firearm to blend in? Well if you are using it in tactical scenarios such as home defense or a red dawn scenario you don't want your firearm to broadcast your presence before you open fire. Surprise in these instances is the best approach. How ever if you are one of those look at me and my cool gun type people then I guess you wouldn't want your gun to be tactical or blend in.
depends on what your hunting. blaze orange shows up as flat grey to a deer for example. Turkey's can see every color possible and have excellent vision.