Before and After

Step 1
Open up your image in PSP.

Step 2
Go to Layer >> New Raster Layer with the Blend Mode on Color Legacy.

Step 3
Using the Selection Tool on the Point to Point setting, make a selection all around their clothing.

Step 4
Now on your Color Palette, choose a gradient that you want to use.

Step 5
Using the Flood Fill Tool (F), fill in the selection with the gradient.