This is from The Symbolic Quest, by Edward C. Whitmont, Princeton University Press, 1969, p.161:

"Projection {of our own shadow material} invariably blurs our own view of the other person. Even when the projected qualities happen to be real qualities of the other person…

Imagine an automobile driver who wears spectacles of red glass. He would find it difficult to tell the difference between red, yellow or green traffic lights and he would be in constant danger of an accident. It is of no help to him that some or for that matter even most of the lights he perceives as red really happen to be red. The danger comes from the inability to differentiate and separate which his "red projection" imposes upon him.

Where a shadow projection occurs we are not able to differentiate between the actuality of the other person and our own complexes. We cannot tell fact from fancy. We cannot see where we begin and he ends. We cannot see him; neither can we see ourselves."