What Causes Blotching Along With Discoloration At The Back Of Calves?

The back of both my calves turned blotchy the almost purple over the last few years. I am a seventy year old healthy male. The itching, especially when exposed to sun would be unbearable. I use witch hazel after my daily shower and hydrocortisone cram, one percent. It helps greatly but the blackening of the skin is cosmetically embarassing. How can I get healthy looking legs back. Thanks, John