The NASA Earth Observatory site shares many incredible images with us, and this image of Laguna Verde in northwest Argentina is amazing!
The various colors of the water are due to a variety of microscopic organisms that live in the lake. According to NASA:
Laguna Verde (58 kilometers wide, 36 km long) often appears green, giving rise to its name. This image shows the turquoise tint in the central sub-basin (image center), with a yellow to black tinge to water in the southern sub-basin (left)—also known locally as Laguna Negro. The northernmost basin (right) appears black. The large gray zone comprising much of the rest of Laguna Verde is likely a combination of shallow water—only inches deep—and sunglint reflecting off the water surface. The reason for the color differences is that many different families of salt-loving organisms occupy hypersaline lakes such as Laguna Verde. These microscopic organisms appear as different colors, often bright, depending on the salinity and temperature of each water body or sub-basin.
You can view it for yourself by loading this KML file
in Google Earth, or visit this page on the NASA Earth Observatory site to learn more.