Does peripheral vascular disease or mixed connective disease cause skin discolaration on any area of the body? Why?

Maybe. Two very different problems. Arterial insufficiency (pad) can cause the skin to be pale, loss of hair below the mid-shin, and cool feet. Blue or black discoloration indicates threatened tissue and can result in amputation if left untreated. Any dark discoloration or non-healing wound(s) should be evaluated by a vascular specialist as soon as possible.