Need image conversion help

Okay artists, please help! I'm working on the TDE user guide. I need some image conversion help. I want to convert some 24-bit PNG images to "locolor." What does "locolor" mean? These are not icons but full images, in case that makes a difference. Is there a definition somewhere of "locolor"? How do I convert/save a 24-bit image as "locolor"? Of all of the various TDE image viewers, how do I view an image's properties to learn about the color depth, etc.? I have tried several (kolourpaint, krita, showfoto, gwenview). I am missing the big picture altogether, probably because I don't know the terminology. Thanks! Darrell