Confused. Would you think I have blood pooling in legs/feet or am I getting purple sitting/standing due to low blood flow? Arterial u/s & pic in file.

Venous blood. With your feet in a dependent position veins become filled with blood that is less oxygenated than arterial blood causing a bluish hue. This is exaggerated if your vein valves are less efficient. This can be an inherited trait with varicose veins seen in family members. If your tissues have normal pink color when your legs are not dependent your blood flow doesn't appear to be abnormal. See a vasc.
Edema. Edema is generally a failure of total circulatory flow. It can be from a weak heart, from weak valves in your veins, or from medications that dilate the blood vessels in your legs. Arterial insufficiency usually leads to cold limbs without edema. Talk to your doc.