I use PSP7, so I know you can do it with PSP

What I do is I use the lasso tool and feather it by like 3 to 5 pixels (or less, just trial and error and what you think looks best).

COPY the selection(s), and leave the selection(s) there.

Go to colors > greyscale and greyscale the whole image

Then go to COLORS > Increase color depth > 16 million

Then go to EDIT > paste > into selection

Viola!