I was a little confused with using a background color... I always have felt that if the map is so rich in color than you dont need to color the background... I tryed a few different backgrounds and found most background colors distorted the view of the blue circles. I agreed on a light background to make sure the North Carolina map makes the most noise. I do like a white background better, but you asked for a background color.
This is my dot density lab... I made 2 maps for this lab... this is the one ill turn in but i think my other one looks way better... just not sure if its what has been asked for.