Camo for wildlife is a hotly debated subject; I know some who swear by it and others who can't stand it. I've also noticed that, least in the UK, most of the older gamekeepers just wear outdoorsy clothing; whilst camo gear tends to be the younger generations. There's also a complicating issue in sight since different animals see differently, plus different weather conditions and lighting and seasons --
Ghilly suits tend to be generally considered workable if somewhat extreme; but otherwise camo is something that at least works to break up your outline if nothing else.
There are a few, but not many lens cover companies out there making camo lens covers for lenses; and honestly for me there are two big bonuses to covers beyond camo.
1) High end lenses are often metal outer bodies - they get COLD in cold weather. With a neoprine cover the insulation means you can hold a lens in the cold for longer wih bare fingers; when its not cold enough to get gloves out but would be if you were holding cold metal all day.
2) Protects against dust*/scratches/marks
Camo patterns are a bonus and I doubt you'll get a sane answer on the battle between dull green jumpers and camo jackets.
I'm not aware of covers for camera bodies; mostly because of all the buttons and such. However there are some rain-covers which fit over lens and body which have a green or camo patterns; and would also be durable and suitable for in the field shooting when you might be in variable weather conditions (even if you've got a high end body with weather proofing the extra layer gives peace of mind at the very least).
*more an issue on the older sigma lenses with their odd roughish coating which shows up loads of scuff like marks