chromatophore

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several types of pigment cells, especially one found in a fish, amphibian, or reptile.
• noun A multicellular organ in cephalopods that contains pigment cells.
• noun A specialized pigment-bearing organelle in certain photosynthetic bacteria.

from The Century Dictionary.

• noun One of the colored masses of protoplasm found in Protozoa.
• noun One of the pigment-cells in animals.
• noun In Actinozoa, one of the brightly colored beadlike bodies in the oral disk of some species, as Actinia mesembryanthemum.
• noun In botany, a name that has been given to the granules which occur in the protoplasm of plants, including the colorless leucoplastids, the green chlorophyl granules or chloroplastids, and the chromoplastids.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A contractile cell or vesicle containing liquid pigment and capable of changing its form or size, thus causing changes of color in the translucent skin of such animals as possess them. They are highly developed and numerous in the cephalopods.
• noun (Bot.) One of the granules of protoplasm, which in mass give color to the part of the plant containing them.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A pigment-bearing cell or structure found in certain fish, reptiles, cephalopods, and other animals.