Both Mr. J2s legs are bluey from a couple of inches below the knee to just above his ankles --- they have been like that for over 30 years, so don't panic. It does mean what you have been told by others and right now we are fighting the NHS to get his veins injected to improve circulation and reduce the strain on his heart (much nagged for appt. is on Friday). He has a triple bypass and does not need any circulatory strain, thank you very much.
If you seek help in these early stages you may fare better than OH, who just accepted it, and now we fight leg ulcers etc. on a very boring, daily long-term basis with pressure bandaging etc. Much better to get it sorted out early. I repeat 'Don't Panic' but try to get it sorted before you get to this stage.