How to have different backgrounds and colors for separators in a gridview?

Question

I want to keep different colors for the separator and background in my GridView. Or I would like to hide the background color visible around the Gridview. I tried changing the layout_margin and padding options, but that didn't change anything. Below is the xml layout for my GridView.

<GridView android:id="@+id/gvFree" android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" android:columnWidth="@dimen/grid_col_wd" android:background="@android:color/darker_gray" android:layout_margin="-5dp" android:padding="-5dp" android:numColumns="auto_fit" android:stretchMode="columnWidth" android:gravity="fill" android:horizontalSpacing="2dp" android:verticalSpacing="2dp" ></GridView> 

Please help.