If you want to reduce your visual impact on the environment, choose a tent with colors that match the landscape you're going to camp in. Green in forest or other vegetated areas, brown for the desert, white for winter camping.
However, if you are in trouble and want to be found, it helps to have a very bright tent that stands out. A tent you can see from kilometers away. A tent that is going to annoy that other backpacker who was just having the illusion to be alone in the world, and now he or she isn't. Such a tent might save your life if rescue agencies are looking for you.
So, to reduce visual impact: choose camouflage. To quicken rescue in emergency: choose anything BUT camouflage.