The vivid colors in the spring are the result of microbial mats around the edges of the mineral-rich water. The mats produce colors ranging from green to red; the amount of color in the microbial mats depends on the ratio of chlorophyll to carotenoids and on the temperature gradient in the runoff. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green.[8] The center of the pool is sterile due to extreme heat.
The deep blue color of the water in the center of the pool results from the scattering of blue light by particles suspended in the water.[9] This effect is particularly visible in the center of the spring due to the lack of archaea that live in the center and the depth of the water.