Interestingly, color wasn’t a consideration to pre-modern Arabs (i.e., the locals), who called the sea ba7r al-qulzum (بحر القلزم) which means “qulzum’s sea” (Qulzum was a place on the Red Sea). read more
Occasionally, the sea becomes filled with blooms of cyanobacteria algae, called trichodesmium erythraeum, which, upon dying, turn the usually blue-green water, reddish-brown. The color is not intense and is said to vary across the expansive body of water. read more