Acrylic works great on leather, and it’s fine to paint and then cut.
Alcohol inks also work well.
One of my favorites for gray / black on leather is to soak 000 steel wool in apple cider vinegar for a few days until it disintegrates, then paint the liquid onto the leather.
The bracelet with the cutouts was colored using the vinegar mixture. The “Resist” bracelet was too, but then I topped it with some pewter-colored alcohol ink to give it a metallic sheen. I finished both of them with a couple coats of Kiwi wax shoe polish.