I tried to use the selective-color technique in the following photo. I added a black&white filter layer with the girl masked. However the right margin of the girl's hand turned out to be white, while there's no additional light source from that direction.
The original photo is posted below.
I have to admit that there's a little bit white on the margin in the original photo. However the white is not that heavy. So I think it must be the
black&white that worsened that margin.