The short answer is that Neptune has the coldest overall average temperature and Uranus has the coldest temperature recorded. The long answer is that once upon a time the answer to this question was simple. Pluto was the planet furthest away from the Sun and also the coldest. However, Pluto was declassified as a planet in 2006 and is now known ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.