What to wear on your legs while deer hunting is rather simple.
If it is warm out, then wear you usual underwear and your camouflage pants.
If it is cool, or cold, out, then wear your usual underwear, usual pants, and camouflage pants.
I don’t bother with long underwear even when it is below zero. Long underwear may help keep you warm, but my fingers, toes, nose, and ears will be very cold a long, long, long time before my body or legs get cold. If it is really cold out, then my feet (my particular cold weakness) will prevent me from staying out long before my legs get cold.
What sort of camouflage pants should you get?
Your hunting pants should be camouflage, the pattern doesn’t really matter. I wear one medium/ heavy pair year round, but if there were more warm days in September , in Wisconsin, then I’d get a light pair too.
The case could be made for scent stopping hunting pants, and its probably better to err on the side of too much scent reduction rather than too little. But if the rest of you is very scent free (you don’t smoke, don’t wear your hunting clothes in public, aren’t sweating, etc), then you would be fine with any ol’ pair of camouflage pants.
Buy camouflage pants that are a few sizes too big. They should easily fit over whatever pants you usually wear.
Over-alls are a good idea if your lower back gets cold while hunting.
My current pair of camouflage hunting pants is excellent. I have an older version of the Scent-Lok TimberFleece pants.
You don’t want to wash you hunting clothes too often because of the UV effects that will happen. Any camouflage pattern is fine, as far as deer are concerned. But some fabrics will glow in low light conditions. There are some UV sprays that prevent some of the UV glow. If you want to see UV glow, then wear your blue jeans outside at dusk on a night with a bright moon, and see your jeans glow.
One last point: buy a dedicated hunting belt for your oversize hunting pants. Your belt should be able to fit around your normal pants and camouflage pants. It should also be a dull color, not make any noise, and not have any shiny metal.