Could you be more specific? What version do you have? If you have version 6.x or higher, have you tried various tabs in the Plot Details dialog under Layer (such as Planes tab) and under Matrix (such as Side Walls)?
With your Profiles plot active, select Format : Page from the menu. Click the Display tab and change the Base Color to whatever you like and click OK. I'f you'd like to make your change for all Profiles plots, then immediately select File : Save Template as.., then click Save and then Yes. All your Profiles plots will show the new background from then on.