Seashell paint makeover: spray paint inside of shells high gloss baby blue and paint outside with gold or silver paint. Maybe could do this with something else from nature if your home isn't beach themed.
Cleaning and restoring colors in seashells.Rinsed in warm water and soak for 24 hours in bleach water. After totally drying, rub each shell with baby oil or with satin varnish to preserve natural color. Gonna clean my shells from the cape this weekend