The Colorful Lakes, or multi-colored lakes, or Telaga Warna in Indonesian, is one of the three main sights on the Dieng Plateau. The lake appears to be a water-filled caldera with several active gas vents below the water's surface, and signs there are sometimes some active vents around the shore. There are usually two lakes, but the smaller one was just a grassy marsh when I visited at the end of the dry season. The smaller lake is usually clear, while the larger one will display bands of color from pale yellow to emerald green, depending on the proximity to the vents.
Shortly after you enter the park surrounding the lake, the trail splits to go around the larger lake. Taking the left trail will take you along the shore of the large lake to the far end, where there is a sort of muddy beach as well as signs of some recently active vents.
The trail to the right leads to a small isthmus that separates the two lakes. The isthmus has a few rocky outcrops and hills that are probably the eroded remnants of the last lava vents. There are several 'caves' in the rocks, although most of them appear to be little more than deep cracks.
Admission to the Colorful Lakes is 9,000 Rupiah (0.54 USD).