Vishuddha (also Vishuddhi) is depicted as a silver crescent within a white circle, with 16 light or pale blue, or turquoise petals. The seed mantra is Ham, and the residing deity is Panchavaktra shiva, with 5 heads and 4 arms, and the Shakti is Shakini.
Vishuddha may be understood as relating to communication and growth through expression. This chakra is paralleled to the thyroid, a gland that is also in the throat and which produces thyroid hormone, responsible for growth and maturation. Physically, Vishuddha governs communication, emotionally it governs independence, mentally it governs fluent thought, and spiritually, it governs a sense of security. In Tibetan buddhism, this chakra is red, with 16 upward pointing petals. It plays an important role in Dream Yoga, the art of lucid dreaming.
Source - Wikipedia