In making a recent LO, I wanted to have an image clipped to a black photo mask with edges tinted blue (bottom right). It took some fiddling to get what I wanted. This is what I learned.
Part 2 of the tutorial here https://ozone.oscraps.com/gallery/showphoto.php?photo=404343&title=colorizing-a-black-photo-mask-tutorial-2c-part-2&cat=all
Final LO and process notes here https://ozone.oscraps.com/gallery/showphoto.php?photo=404271&title=stressed&cat=all and here https://ozone.oscraps.com/gallery/showphoto.php?photo=404273&title=colorize-mask-process-notes&cat=all