I have noticed recently my right leg and foot is significantly darker and duskier when standing. i had plantar fascitis in right foot a few months ago?

No correlation: There is absolutely no correlation to skin discoloration and plantar fascitiis. The word "dusky" in medical terminology indicates a dangerous situation associated with poor circulation. You may be misusing the word or it might be the case. But, since i can't see it, i would advise you to see a doctor.

Circulation problem: You need to see your doctor, podiatrist, or vascular or heart surgeon immediately as this is usually a sign of some form of circulation blockage like a blood clot.