There is small volcanic Island called Flores in Indonesia which contains a volcano called Kelimutu.
This volcano has formed three crater lakes which change colour from white, green, blue and brown to black.
This colour change can be explained on basis of chemical composition as well as microbial growths.
Usually volcanic has greater composition of metallic elements such as iron and manganese. These metallic elements are oftentimes oxidised or reduced due to many factors such as climate, underground water systems of the volcano itself and volcanic gas output.
The other reason behind colour change of lakes might be due to microbial growth due to varying chemical composition of the water. For example green colour of the lake is produced by rapid algal growth in the spring months. However, soon after it is followed by clear water phase as zooplankton emerge and consume algae.
The beauty of the lakes are absolutely at the zenith of serenity.