How do brown algae get their brown or olive-green color?

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“mermaid's wine glass” algae — Algae The macroscopic genus of algae known as *Acetabularia* is commonly called “mermaid's wine glass” because of the distinctive umbrella-like shape of the tips of its stalks.

The color of brown algae (class Phaeophyceae) ranges from dark brown to olive green. This variation is determined by the specific proportion of two types of pigments present within the organism:

Fucoxanthin: A brown carotenoid pigment.12
Chlorophyll: The green pigment used for photosynthesis.13

While chlorophyll typically absorbs red and blue wavelengths—making plants appear green—the presence of carotenoids allows these algae to absorb additional light, particularly in the green and blue parts of the spectrum. The final appearance of the alga is simply a result of the balance between these brown and green pigments.231