I used Corel PHOTO-PAINT 10. As far as the steps it is just a matter of playing with the mask and fill tools.
After opening the file, use mask invert to reverse the masked area, fill with whatever color you want.
Invert the mask again.
Expand it by one (or however many) pixels you want. You could stop here and get the same effect.
To clear out what you don't want. Invert the mask again, and hit DEL or clear the extra stuff (background) out.
Invert the mask one more time, back to just around the items and save the file.
That's it. You could write a script to run this in a batch process, but it was just as easy to do them by hand and it was relaxing - not too much to think about.
Glad you like them.
Kuv