At close range of 20 yds or less, you need to conceal your outline. The deer notice odd things that don't seem to belong. My best success at close-range ground hunting is when I am behind some trees in a blind that is not sticking out like a sore thumb. As many will say here, your movement will get you busted more than anything. Also sound will put them on alert. And scent more than anything.
For long range with a gun of 60+ yds, camo is not a factor so much. In fact we have to wear blaze orange. Still, it is helpful to at least be able to conceal half your outline behind a tree and keep movement and noise to a minimum.