Make the defaults actually work properly.

overviewer_core/src/primitives/overlay.h

@@ -24,7 +24,11 @@ typedef struct {
 typedef struct {
     /* top facemask and white color image, for drawing overlays */
     PyObject *facemask_top, *white_color;
+    /* color will be a pointer to either the default_color object below or
+       to a specially allocated color object that is instantiated from the
+       settings file */
     OverlayColor *color;
+    OverlayColor default_color;
     /* can be overridden in derived classes to control
        overlay alpha and color
        last four vars are r, g, b, a out */