Pharaoh cuttlefish they can show a mottled white and brown color, with a center circle of brown. The mechanism for color is the same in the Pharaoh cuttlefish as it is in other cuttlefish. This colour-changing function is produced by groups of red, yellow, brown, and black pigmented chromatophores above a layer of reflective blue and green tinted iridophores and leucophores, with up to 200 of these specialized pigment cells per square millimeter. These sacs of color are controlled by rings of muscle around the sac. The cuttlefish expands and contracts these muscle rings in order to show different colors. It is
Road signs in the United Kingdom patch may only be coloured blue or green. Signs indicating a temporary change, such as roadworks or route diversions, are denoted with a yellow background. Usually these signs use a simple black on yellow colour code, more complex signage use the conventional signs superimposed onto a yellow background. In some areas, such as the Dartmoor National Park, additional signs and colours are used to distinguish road conditions. In addition to the national colour schemes, the park also uses white signs with a light blue border and text to denote routes suitable for medium-sized vehicles and white signs with a brown