Save yourself some money and get a little single-use packet of automotive brake caliper grease. It's silicone based and will not deteriorate the rubber or silicone o-rings. A packet usually costs a dollar or so and will outlast your engine most likely. Putting stuff on your o-rings whether it be green slime or anything else isn't going to seal the needle. If it leaks anything, fuel will leak OUT, not air leaking IN. Also, a needle that's well lubed may move changing mixture settings while the engine runs. If you lube the o-rings, do so sparingly.

Ive had NO need to put anything on my needle o-rings. They don't leak and hold a setting fine. Just my opinion though.