The Colour Out Of Space is a short story written by H. P. Lovecraft. I would not consider it to be one of his better stories, but it's certainly one of the more well known ones. It is also the source of many people's misconceptions about the nature of his writing (The descriptions in this story are somewhat repetitive, and describe things as "impossible to describe", which to many sounds like a cop out.)
Spoiler Warning!
The story is told from the point of view of a surveyor who is commissioned to survey some disused land to be flooded by a reservoir. He arrives in Arkham having heared strange tales of creepy supernatural goings on, but as a man of science, he does not believe it at first. Once he has seen the color however, things change. The whole story is permeated by a vein of uncertainty because the community in question is both tight lipped and superstitious, so they don't talk much, and when they do it can be hard to filter truth from legend.
The story centers on an unspecified New England town called Arkham where a strange meteor lands and brings with it a substance than defies all known laws of physics (the story is set in the 1880s). The substance is a soft solid that remains hot and slowly dissipates away over time. The substance does not react to solvents, acids, or bases, and (you guessed it) is an indescribable color than no two people percieve the same way. There are other strange properties to this substance which become apparant later.
The meteor slowly dissolves, and its eerie color creeps slowly through the nearby fields and orchards, making the produce inedible and altering the soil such that all plants and animals grow differently (but in a manner that defies description). Over the next year or so, the crops go bad, all the animals are spooked and behave strangely, the farmer who farms the land where the meteor hit and his family go mad and waste away. The land remains abandoned and is named "blasted heath" by the locals.
In conclusion, it isn't all that bad of a story if you can get past half of the things in the story being described as indescribable. There are a couple things that I got wondering about reading it from a modern viewpoint.
- Could the substance be radioactive? At the time of publication (1927), people didn't know all that much about the effects of radioactivity on living things.
- Is it really a good idea to flood this contaminated land and then drink the water. In the story everybody is glad to cover the site up, but there is no mention of people being wary of the effects on the water. It is quite possible that the reader is supposed to worry about that part on his or her own.