Change spinner background color but keep arrow

For the record, I found an easy solution : Wrap your spinner in a relative layout and add an image :

 <RelativeLayout 
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:background="@drawable/borderbottom_white"<!-- white background with bottom border -->
     android:layout_marginTop="15dp"  >
        <Spinner
        android:id="@+id/postfield_category"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="16sp"
        android:background="@null"
        android:minHeight="0dp" />
        <ImageView 
         android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:src="@drawable/arrowspinner" />
    </RelativeLayout>

A simple solution that doesn't require you to create your own drawable for the arrow is to wrap the spinner with a RelativeLayout, and set the background color in the RelativeLayout, not the spinner:

<RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#f00" >
    <Spinner
        android:id="@+id/spinner1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

Use this:

yourspinner.setOnItemSelectedListener(this);
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
        long arg3) {
    ((TextView) yourspinner.getSelectedView()).setBackgroundColor(getResources()
            .getColor(R.color.your_color));
}

and your class should implement OnItemSelectedListener.

I did a little modification based on @Mansur Khan 's answer.

We don't have to add an ImageView in this case because the spinner already has a triangle arrow. So check the code below:

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="8dp"
        android:background="#FFFFFF">
        <Spinner
            style="@style/Widget.AppCompat.DropDownItem.Spinner"
            android:layout_width="match_parent"
            android:layout_height="70dp"
            android:id="@+id/sign_up_country"
            />
    </RelativeLayout>

Here is the screenshot

Before:

After: