Color pop

It is sometimes called "selective color" or "spot color." The classic example is the red coat in Schindler's List, but the technique works for any photo with a clear subject (people, pets, products, food).

Yes. The AI segments the foreground subject from the background. Photos that are mostly background (landscapes, skies, abstract shots) end up entirely black-and-white because the model finds nothing distinct to spare.

Not in this tool. If you want the inverse, use Remove Background to cut out the subject, then composite it manually in an editor like Photopea or Photoshop.