The Bottom 1/3 Of My Legs (both) Have Been Discolored,

The bottom 1/3 of my legs (both) have been discolored, a reddish-brown color for several months now. Almost like leftover tanned skin that will not go away.I wear ankle socks all the time, and the discoloration pretty much stops at the top of the socks. I drive a minivan all day, transporting medical patients, I'm 6', and heavy.. abt 285lbs. W/Male, 61 years old.