[R-sig-Geo] Altering Quadrat count plot specifications

[Abby Rudolph]

I am able to calculate and plot the quadrat counts for my cases and controls, however, the background of the map is by default colored with blue at the top and peach at the bottom.  Is there a way to change the default coloring scheme of the plot background (e.g., the area of the shapefile window) to either be blank or to reflect the coloring scheme in the spatial intensity maps produced with density?

Second, I was also hoping to create a map where quadrats with cases but no controls were one color, quadrats with controls but not cases were a second color, quadrats with cases and controls were a third color and quadrats with no cases and no controls were a fourth color.  Is this possible?  Right now, I subtracted qcases from qcontrols, so I can plot this difference (however, it is misleading due to the zeros).  I can also quantitatively tell how many regions fall into these categories.  For example cases_but_not_controls<-sum(qcases&!qcontrols)
Of 60 quadrats, 4 have cases but not controls, 6 have controls but not case, 11 have both, and 40 have neither.
Any assistance would be greatly appreciated!

Thanks in advance!