Why are some multicellular algae called brown red?

Multicellular algae come in three colors. They are green, brown and red. Color differences are caused by the different depths of the water’s habitat, as well as the number of particles in the water itself. Green algae photosynthesize. Because of this, they are green. But for this there must be a sufficient amount of sunlight. Brown and red algae live quite deeply, where there is either very little or no sunlight. Therefore, they are not capable of photosynthesis. They receive organic matter in other ways and have correspondingly different colors.