Just 150 years ago, Yellowstone's magnificent geothermal pools were likely a plain blue hue -- not a reflective canvas of rainbow colors.

In a new study, published last week in the journal Applied Optics, a team of researchers was able to reconstruct the spectral history of Yellowstone's Grand Prismatic Spring, Sapphire Pool and Morning Glory Pool via computer modeling.

The scientists were able to determine that Morning Glory Pool was not always the impressive array of yellow, greens and blues that is today. The cacophony of colors, in fact, is mostly the result of human impact on Yellowstone's geothermal ponds.

"As a result of coins, trash, and rocks thrown into the pool over time, the vent has become partially blocked, leading to a lower temperature and altered color pattern," the study's authors wrote in the newly published paper.

Specifically, the prism-pattern colors seen in today's geothermal ponds are the result of expansive communities of microbes. These microbial colonies collect in mats -- spurred by the ideal growing conditions and toasty temperature of the thermal water, which fluctuates between 140 and 194 degrees Fahrenheit.

While shallow color variations are mostly the result of these microbial mats, the basic physics of light absorption and scattering in the deeper portions of the pond add to each body of water's visual diversity.

The new study is the first to show empirically how physical and chemical variables in geothermal pools affect their optical appearance. Researchers originally built the model for fun, but quickly realized there was very little hard science on the subject.

"What we were able to show is that you really don't have to get terribly complex -- you can explain some very beautiful things with relatively simple models," Joseph Shaw, a computer engineer at Montana State University, said in a press release.

"Our paper describes a very simple, 1-dimensional model, that gives the first clue if you really want to do more," said German researcher Michael Vollmer.

"We didn't start this project as experts on thermal pools," Shaw added. "We started this project as experts on optical phenomena and imaging, and so we had a lot to learn."