where is it found?
The entire Northern Hemisphere including most of North America, Europe and Asia plus parts of Northern Africa.
Red fox
The red fox ("Vulpes vulpes") is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia plus parts of Northern Africa. 
do red fox change color in the winter Yes,  A typical colouration in red foxes usually represents stages toward full melanism, and mostly occurs in cold regions.
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Red fox [SEP] Introduction
The red fox ("Vulpes vulpes") is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia plus parts of Northern Africa. It is listed as least concern by the IUCN. Its range has increased alongside human expansion, having been introduced to Australia, where it is considered harmful to native mammals and bird populations. Due to its presence in Australia, it is included on the list of the "world's 100 worst invasive species". The red fox originated from smaller-sized ancestors from Eurasia during the Middle Villafranchian period, and colonised North America shortly after the Wisconsin glaciation.