This book offers a comprehensive exploration of bio-optical variability and ocean color remote sensing in India’s coastal waters. It highlights the importance of satellite-derived chlorophyll-a for monitoring ecosystem health, detecting algal blooms, and supporting fisheries, emphasizing the need for region-specific calibration. The complex optical properties shaped by freshwater influx, river discharges, and seasonal monsoons are examined, with a focus on differences between the Arabian Sea and the Bay of Bengal. The role of phytoplankton dynamics, CDOM variability, and particle size structure is analyzed to understand ecological processes and human impacts. Case studies from diverse coastal environments, including estuaries and river plumes, illustrate the use of remote sensing in tracking productivity, pollution, and water quality. The progress in Ocean Colour Remote Sensing in India, supported by training and institutional efforts, is also discussed. This work aims to advance sustainable management and scientific understanding of India’s diverse and dynamic coastal ecosystems.