The first time Stanley is shown on screen his hair is gray and white all over. The next time Stanley is shown in the police station his hair is brown with gray only visible on his temples. In other scenes of the film his hair changes color from gray/white to brown with graying at the temples.
When Connie is in the bathroom before she is killed by intruders, there are 2 red spots on the lens, one on the right and one on the left. These are probably from a previous shot where fake blood got splattered on the camera lens and the operator failed to notice it.
After Connie is killed in the bathroom and Kearney and Lou enter Stanley's house to serve him papers, we see the outline of Connie's body with fresh blood on the bathroom floor. Blood turns a darker/brownish color after it is exposed to air, especially the time it took after Connie's murder and the beginning of this scene.