Photoshop repair Picture: color background black and white characters

We all know the pictures of the characters are mainly skin color in the R version, as long as the background is almost no red, to achieve Photoshop figure color background black and white is basically not three minutes to finish.

We all know that the people who take pictures of them are the main colors in R.
As long as the shooting background is almost no red state
To reach the Photoshop figure the color background black and white is basically not in three minutes to finish

How do we come to see

1.

2.

3.

4.

5.

6.