Hi

Noob question. I was browsing the files of character templates contributed by various artists. 

The layers of PNG files are like naked body of character, another layer could be various hairstyles, various hats or various clothes. What kind of software can I use to edit these files, e.g. to add or change the color of the clothes or to combine the layers together?

I am a hobbyist, so I am looking for a freeware software to do this. Thanks.

The best, Free and open-source, image editing program is Gimp.

The other option would be Krita, but it's designed more as a drawing program than an image editing program.