The ocean color remote sensing is used to retrieve the water constituents such as phytoplankton generally from satellites observations. However, it is still difficult to apply this technology for the coastal regions, due to the low spatial resolution of the sensor, the limited observation periods. To address these problems, we newly developed a compact multi-band spectral imaging sensor, which is suitable for coastal ocean color remote sensing by a drone. In this paper, we experimentally evaluated our coastal ocean color observation system in Suruga Bay in Japan. The result showed the spectral shape of observed ocean color exhibited the typical color of case II water. Finally, we briefly introduce the latest-version of our radiometer.