The shell of the cockle which is the common name for a group of small edible saltwater shellfish – clams. Cockles bury themselves into the sand, opening up to feed from the plankton in the water ; they can be collected for food at low tide.
Cockle shells in many sizes and in broken shards are easily collected on beach combing trips from any sheltered sandy beaches around the world.
The many tones and hues that go to make up the colour scheme of a cockle shell would be impossible to intuit from just the shade card.
The visual subtlety gained from this complexity of colour and form can only be found in the natural world.