nnguye20, if these spots are made of carving dust, they must be easy to remove with water. If you can't, maybe that's a mix of dust and other thing, a glue for exemple, then, try to rub spots with acetone, and more softly with alcohol (alcohol would remove an acrylic painting).
Sometimes, tahitian pearls have little white spots, but these lacks don't look like these you are showing, specially the one on pearl in the middle.
Try also to rub spots with your nail: if nacre goes away like a powder and you feel you dig nacre, doing that, it's a bigger problem. That means nacre has been damaged in depth by some chemical (for exemple, toluene makes that, and also new glues used to stick glass under sunlight catalysis).
About colours of carving, each tahitian pearl is different.