Purple spots appear on the underside of a new patio cover (GAF roof) when it rains. Both the roofer and a GAF inspector can't figure out what is causing it. They appear in one area of the cover. This same area was getting green spots with rain after their first installation (it leaked and they had to replace it) Now they are purple, many more and much bigger. Time after time this roofer has had to come back to "fix" things that weren't done properly since the initial installation of ...»