@peadar You are right, both green and black have a significance in Islam and green is the colour most strongly associated with Islam. This from https://classroom.synonym.com/what-are-the-colors-of-islam-12086654.html:
"Green has represented Islam for centuries. Many Islamic countries such as Saudi Arabia and Iran feature the colour green on their national flags. Some believe that green was the Prophet Muhammad's favourite colour, and it is mentioned in a number of verses in the Quran as the colour that will be worn by the inhabitants of paradise.
Black
During the period of the Islamic Caliphate, warring factions took on certain colors to represent themselves. When the Abbassid Caliphate revolted against the Umayyads, they wore black clothing and carried black battle standards as it was thought that the coming of the messiah would be signified by a man with a black banner. Today in Iran, devout Shiite women wear black chador and ayatollahs wear black cloaks, while certain descendants of the Prophet Muhammad wear black turbans."
"Green has represented Islam for centuries. Many Islamic countries such as Saudi Arabia and Iran feature the colour green on their national flags. Some believe that green was the Prophet Muhammad's favourite colour, and it is mentioned in a number of verses in the Quran as the colour that will be worn by the inhabitants of paradise.
Black
During the period of the Islamic Caliphate, warring factions took on certain colors to represent themselves. When the Abbassid Caliphate revolted against the Umayyads, they wore black clothing and carried black battle standards as it was thought that the coming of the messiah would be signified by a man with a black banner. Today in Iran, devout Shiite women wear black chador and ayatollahs wear black cloaks, while certain descendants of the Prophet Muhammad wear black turbans."