Source: http://io9.com/these-color-swatches-coul...

For the first time ever, scientists have created a detailed catalogue of color swatches that correspond to nearly 140 known microorganisms, including those that can live in the most extreme environments. Armed with this knowledge, astrobiologists can now scan the atmospheres of distant exoplanets in hopes of finding a match.

"This database gives us the first glimpse at what diverse worlds out there could look like," noted astronomer and study co-author Lisa Kaltenegger in the Cornell Chronicle. "We looked at a broad set of life forms, including some from the most extreme parts of Earth."

Indeed, as witnessed on our planet, the history of life involves microbes. Lots of microbes — enough to influence the reflective signature of our planet when seen from a distance. The Cornell astronomers conjecture that a similar thing must happen on other habitable planets, and that life evolves through single-celled stages prior to multicellular creatures. Their database, which is freely available here, is the first to catalogue the spectral biosignatures that would be generated by such life.