Distance/curvature of the earth. If you were in the Navy, you know roughly how far away the horizon is. Add in buildings, roads, hills...etc. Easy to not see the launch especially if it was 10 miles offshore.
I've participated in night missile shoots and they are unmistakable. They flash of the launch can be seen for miles and the missile itself shoots out a flame as long as a telephone pole. Yet nobody reported seeing anything like that. Why not?
Again, distance. Most of the witnesses were miles away. How big is a telephone pole at 10+ miles? As for different compass headings of the missile trajectory it would just mean the witnesses are seeing it from different points of view and the color differences would be caused by local atmospheric conditions and angle of the rocket plume (brighter and whiter from the rear, for example)