Color of Murex Shells Being from Sea Fouling Organisms

The picture of a murex with outer shell looking like stripes of dark blue green (like the sea), and the inside stripes of red and white featured on Is that the sea fouling organisms covering them, or is it its natural color? Because I’ve seen in other places the color being light brown.

The color of the snails shell after it’s been polished in beige to brown. I have never seen a snail with this color in the ocean or in an aquarium. The snails grow in the water, and naturally have sea fouling grow on them. The sea fouling is whatever color the sea bottom is. I’ve seen blue, blue-green, purple, and brown. – Mois Navon.