Why is a green dot brighter than a red dot?

Hello guys, lately I have been asking alot of questions and I'm sorry about that. My favorite hobby is lasers and I have been amused by them my whole life. I have 3 questions. Why is a 5mW green dot brighter than a 5mW red dot? And my other questions are, if I point my 5mW green laser at a black surface it's not bright at all. But when I shine it at a white or lighter color surface such as a wall it is very bright, Is is bad to look at when it's on a white wall or lightly colored surface? I'm just asking this because when I look at the green dot on a brightly colored surface it leaves a black dot in my eyes. Like when you stare at the sun for a second and then blink. I'm just concerned and could use some of your help. Thanks
Cb19

A quick search would have answered this

http://laserpointerforums.com/f50/how-many-times-green-brighter-than-red-36744.html

Oh sorry about that. Is the dot on a white wall dangerous to my eyes?

Green is more visible to the human eye than the colour red.

If it's around 5mW you should be fine, unless the wall is glossy white, unless if you're looking at the dot point blank like--