Edit a Single Layer

[hammonjj]

I'm extremely new to photoshop, so please bear with me.

I'm trying to colorize a photo. It's a picture of a guy riding a bike and I want him in color and the rest of everything with a saturation of 0. I used the magnet lasso tool and outline the dude on the bike, created a new layer and pasted him there. Then I went to my background layer, turned the saturation to 0 and this worked wonderfully. Now, I want to turnt he saturation to 0 on certain parts inside of the man. I can see the background in between his arms, legs, etc. I tried to lasso the part I want, created another new layer and pasted it there. I want this new layer to also have a saturation of 0, but when I turn it to zero, it effects the layer beneath it. Does this make sense?

How do I just change the color of a single layer?

[pswift]

Don't copy and paste. Instead select what you want, then create a new Hue & Saturation adjustment layer and Photoshop will automatically create the proper mask so that the adjustment layer will only affect that particular selection. Read more about masks too, they are one of the most useful features in Photoshop.