That's fun Francois. It needs something in the image like a person, the sky or vegetation. If it doesn't know what color something should be it gives it a very muted color or leaves it black and white. I took a color photo, converted it to black and white then let it turn it back to color. It didn't do too bad, it could have put more blue in the water. Obviously it didn't know that there was red in her strap but it did do surprising well with her hair color.