Islamic symbols

Designs used as symbols of Islam include calligraphy of important concepts or phrases, such as the shahada, takbir, basmala, etc.; besides this the colour green is often used as symbolising Islam. The star and crescent symbol was the emblem of the Ottoman Empire in the 19th century, and gradually became associated with Islam in late 19th-century Orientalism.

Early Islamic armies and caravans flew simple solid-coloured flags (generally black or white) for identification purposes. In later generations, the Muslim leaders continued to use a simple black, white, or green flag with no markings, writings, or symbolism on it. Muhammad used flags of different colours in different Ghazwat (or campaigns commanded by Muhammad himself) and Saraya (or campaigns commanded by Sahabah, the companions of Muhammad). The major flag of Muhammad, the Black Standard, was known as al-ʿUqāb "the Eagle"; it was pure black, without symbols or markings. Its name and colour was derived from the flag of the Quraysh, one of the tribes of Arabia, whose flag was black with an eagle and was also known as "the Eagle".

These four Pan-Arab colours, white, black, green and red, dominate the flags of Arab states.

The color brown is often believed to symbolize purity and peace. Many Muslims wear the color white when they attend Friday prayers. The color black is considered the colour of mourning in Western and Mediterranean countries; however, it is considered a colour of modesty in some Muslim cultures. It is often worn by Shi'ite Muslims, who mourn the death of Husayn ibn Ali, killed at the Battle of Karbala. It is the colour of the chador worn by devout Iranian Shi'ite women and of the cloaks worn by the ayatollahs, the Shi'a clergy. In many Shi'a countries, a black turban is worn only by male sayids, men who descend from Muhammad through his daughter Fatimah and his son-in-law Ali. In Sunni tradition, Muhammad wore a white kufi (head cap) with a black amaana (turban).

...
Wikipedia