Photoshop :: Color Picture To Color + Black And White

I have a color picture which I took, of a red berry bush. I want to remove all the color except for the red from the berries. I know how to lasso the berries, but I can't remove the color from the bush/background and leave the red berries.

Note: I did this once a couple years ago, and can't remember how I did it..I have some memories, but probably remember just enough to make me dangerous. I have done some searches but obviously the results are numeorus and I haven't found what I am looking for yet.

I know the solution involves selecting the berries and then inversing it and then setting all 3 colors to 0 for the background.

What I can do is
1) lasso the berries

2) inverse
what I can't figure out
1) it seems like there was 1 step about layering which enabled me to get started, but I don't remember this, it does seem like I am missing something very basic when I try to do this

3) Where is the color scale, the only thing I can find is the grayscale option which switches the entire project to black and white.