Prov. People whose hands are usually cold have kind and loving personalities. Nancy: I don't like holding hands with Joe. His hands are so cold. Jane: Cold hands, warm heart.
Not showing one's feelings does not signify lack of feeling. For example, Dan rarely sends flowers or anything, but he's a case of cold hands, warm heart. Why a literally cold hand should indicate sympathy or affection is not really clear, but this expression has been so used since about 1900, and the Germans have an identical saying ( kalte Hand, warmes Herz).