A lot of the time, guys don't know what "natural" is, because they have probably never seen a girl without makeup in their life (even if she isn't wearing "makeup", she might still be wearing tinted moisturizer/BB cream, a natural shade of blush, clear brow gel, one coat of mascara, a lip stain etc).
Depends on the situation. For everyday life, I like light makeup. Just basic stuff to look "fresh" and "awake."
For evening wear, I like a little more daring makeup. Smokey eyes, a little color on the lips. The one thing I don't like is bright red lipstick. I think darker reds are sexy, but bright red has always been a turnoff for me. I know it's classic, but I've never liked it.
I also like the occasional weird shade - purple lipstick, green eyeshadow, etc.
I have an untested hypothesis that wearing makeup actually damages your face, thus making it impossible to look presentable unless makeup remains in use, to keep you buying.
That being said, au naturale is the way to go for me. From the day I met her to present day, my wife has never used makeup and still looks beautiful as ever.
There are a couple of secrets she has used though. 1. Stay out of the sun. Wear a wide brimmed hat if you're going to be out in the sun. The best time to get your "vitamin D" if you aren't drinking it in milk or vitamins anyway, is the last hour before sunset and you won't need sun protection at that time.
2. Drink lots of water. Thoroughly hydrate yourself.
Most of the time I prefer the Au Naturale, as that will enhance a females skin a lot further in life. There are those kinds of females who don't need to wear make up and I find them to be more attractive. Then there are those who wear light make up, they too are ok in my book as long as they know how to put it on.
The truth is, men want to think they're seeing us as we really are. This is why they like us wearing light makeup. It looks natural, but it's neat and polished. Heavy eyeshadow and bright red lips, on the other hand, probably make him wonder what we'll look like in the morning. It's just too far from our natural look.
My guy prefers no makeup. He says I look better without it, but I doubt that. They'll say anything to make you happy -- just do what you wanna do, girl! Wear what you wanna wear, and say fuck it all to those who make shitty comments about you!