Exactly what causes the red color of the algae is not yet completely clear, according to the French researchers who are now studying the species.
However, the color is probably a way for the algae to protect themselves from the sun.
In the same way that humans get sunburned, the algae probably change color from green to red when exposed to strong sun, Eric Merechal explains.
However, the color is not the only mystery that the researchers want to solve.
- What we mainly want answers to is where they come from.
In the mountains we always have white snow, but suddenly we started to see this algae.
Where was it before?
That is the big question, Merechal told Reuters.
Makes the snow melt faster
One theory is that global warming has made it possible for the species to gain a foothold in the Alps.
The hotter it is, the more algae appear, says Alberto Amato, who researches genetic engineering at the research center in Grenoble.
Researchers have also been able to establish that the algae cause the snow to melt faster, as they prevent the sun's rays from being reflected to the same extent.
- It's a bit of a vicious circle.
"Now we are trying to understand all the mechanisms so that we can do something about it," Alberto Amato told Reuters.
See pictures from the researcher's work in the Alps in the clip above.