Help With Guppy

[FishPerson]

My female guppy that I just bough today suddenly turned black, sank to the bottom of the tank and stopped moving.

 

[PrairieSunflower]

I've not heard of this happening before.  What color was your guppy before it turned black?
 
Could you tell us a bit about your tank, size, filtration, temperature, how long has the tank been cycled/has the tank been cycled, do you use dechlorinater, readings (ammonia, nitrite, nitrate), other tank mates. 

 

[FishPerson]

I have other guppies in the tank but they seem fine. It was something like grey before it turned black.

 

[PrairieSunflower]

If you could answer the above questions... also, provide a photo.
 
Could it also be that in transport the fish had faded (which is not unusual during stress or if kept in the dark) and just darkened as she adapted to the light again?

 

[FishPerson]

The fish is fine now, so I'm assuming that I over reacted.

 

[PrairieSunflower]

Ok.  Probably was just scared.  No worries, I flip out too.