The color green has a special place in Islam. It is used in the decoration of mosques, the bindings of Qur'ans, the silken covers for the graves of Sufi saints, and in the flags of various Muslim countries. Green has been associated with Islam for many centuries. The color green was the color used by Muhammad’s tribe on their flags. According to Muslims the colour green symbolizes nature and life.
The crescent was not a symbol used for Islam by Muhammad, as Islam is against appointing "holy symbols" (so that during the early centuries of Islam, Muslim authorities simply didn't want any geometric symbols to be used to symbolize Islam, in the way that the cross symbolizes Christianity, the star of david was a commonly occurring symbol of Judaism and Jews, etc.). This is why early Islamic coins were covered with Arabic writing, but contained no other visual symbols
Allah is the Arabic word for God (literally 'the God') It is used mainly by Muslims to refer to God in Islam.
The hamsa is a palm-shaped amulet popular throughout the Middle East and North Africa, and commonly used in jewelry and wall hangings. Depicting the open right hand, an image recognized and used as a sign of protection in many societies throughout history, the hamsa is believed to provide defense against the evil eye. The symbol predates Islam. In Islam, it is also known as the hand of Fatima, so named to commemorate Muhammad's daughter Fatima Zahra.
The Rub el Hizb is a Muslim symbol, represented as two overlapping squares, which is found on a number of emblems and flags. In Arabic, Rubʻ means "one fourth, quarter", while Hizb means a group. At first, it was used in the Quran, which is divided into 60 Hizb (60 groups of roughly equal length); the symbol determines every quarter of Hizb, while the Hizb is one half of a juz'. The main purpose of this dividing system is to facilitate recitation of the Qur'an.