I’ve used the Spike It dies for years and they work great on smoke, pumpkin, watermelon colored baits. I’ve never done it to black worms mainly because I’m using a different profile bait like a jig or just stick with plain black if water is that stained.
If your point is to totally change a color with paint it won’t do that but giving the bait a bright tail it does a great job of. It doesn’t look obvious in your hand but really shows when put into the water.