[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] MattBooth:
You could also include this:

\res\layout\tw_status_bar_expanded.xml

Find in red, change to blue

TWO Edits here:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout android:id="@id/notification_panel" android:background="@drawable/notification_panel_bg" android:paddingTop="@dimen/notification_panel_padding_top" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_marginLeft="@dimen/notification_panel_margin_left"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:systemui="http://schemas.android.com/apk/res/com.android.systemui">
<FrameLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_marginBottom="@dimen/close_handle_underlap">
<include android:layout_width="fill_parent" android:layout_height="@dimen/tw_notification_panel_header_height" layout="@layout/tw_status_bar_expanded_header" />
<TextView android:gravity="center" android:id="@id/emergency_calls_only" android:paddingBottom="4.0dip" android:visibility="gone" android:layout_width="fill_parent" android:layout_height="wrap_content" />
<HorizontalScrollView android:id="@id/quicksetting_scroller" android:scrollbars="none" android:layout_width="wrap_content" android:layout_height="@dimen/quick_setting_button_height" android:layout_marginTop="@dimen/tw_notification_panel_header_height">
<com.android.systemui.statusbar.policy.quicksetting.QuickSettingPanel android:orientation="horizontal" android:id="@id/quicksetting_container" android:layout_width="wrap_content" android:layout_height="wrap_content" android:divider="@drawable/tw_black_bg" android:showDividers="middle" />
</HorizontalScrollView>
<ScrollView android:id="@id/scroll" android:fadingEdge="none" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_marginTop="@dimen/notification_panel_quicksettingbtn_height" android:overScrollMode="ifContentScrolls">
<LinearLayout android:orientation="vertical" android:id="@id/scrollCart" android:layout_width="fill_parent" android:layout_height="wrap_content">
<LinearLayout android:orientation="vertical" android:id="@id/brightness_controller" [COLOR="Red"]android:background="#[COLOR="Blue"]00[/COLOR]000000"[/COLOR] android:visibility="visible" android:layout_width="fill_parent" android:layout_height="56.0dip">
<LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="55.0dip">
<ImageView android:id="@id/brightness_icon" android:clickable="true" android:layout_width="25.0dip" android:layout_height="fill_parent" android:layout_marginLeft="13.0dip" android:src="@drawable/ic_sysbar_brightness" android:contentDescription="@string/accessibility_brightness_icon" />
<FrameLayout android:id="@id/brightness_group" android:layout_width="fill_parent" android:layout_height="fill_parent">
<com.android.systemui.statusbar.policy.ToggleSlider android:id="@id/brightness" android:layout_width="fill_parent" android:layout_height="fill_parent" systemui:text="@string/status_bar_settings_auto_brightness_label" />
<com.android.systemui.statusbar.policy.ToggleSlider android:id="@id/auto_brightness" android:layout_width="fill_parent" android:layout_height="fill_parent" systemui:text="@string/status_bar_settings_auto_brightness_label" />
</FrameLayout>
</LinearLayout>
<View [COLOR="Red"]android:background="#[COLOR="blue"]00[/COLOR]091a24"[/COLOR] android:layout_width="fill_parent" android:layout_height="1.0dip" />
</LinearLayout>
<LinearLayout android:orientation="vertical" android:id="@id/noNotificationsTitle" android:focusable="true" android:layout_width="fill_parent" android:layout_height="wrap_content">
<TextView android:textSize="@dimen/status_bar_expanded_notification_category_text_size" android:textStyle="bold" android:textColor="@color/notification_category_color" android:gravity="left|center" android:id="@id/noNotificationsText" android:paddingLeft="11.0dip" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_expanded_notification_category_height" android:text="@string/status_bar_no_notifications_title" />
</LinearLayout>
<LinearLayout android:orientation="vertical" android:id="@id/onGoingCart" android:background="#ff293945" android:focusable="true" android:visibility="gone" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_expanded_notification_category_height">
<TextView android:textSize="@dimen/status_bar_expanded_notification_category_text_size" android:textStyle="bold" android:textColor="@color/notification_category_color" android:gravity="left|center" android:id="@id/onGoingNotificationText" android:paddingLeft="11.0dip" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/status_bar_ongoing_events_title" />
</LinearLayout>
<com.android.systemui.statusbar.policy.NotificationRowLayout android:id="@id/onGoingItems" android:layout_width="fill_parent" android:layout_height="wrap_content" systemui:rowHeight="@dimen/tw_notification_row_min_height" />
<LinearLayout android:orientation="vertical" android:id="@id/notificationCart" android:background="#ff293945" android:visibility="gone" android:layout_width="fill_parent" android:layout_height="@dimen/status_bar_expanded_notification_category_height">
<RelativeLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content">
<TextView android:textSize="@dimen/status_bar_expanded_notification_category_text_size" android:textStyle="bold" android:textColor="@color/notification_category_color" android:gravity="left|center" android:id="@id/latestNotificationText" android:paddingLeft="11.0dip" android:layout_width="180.0dip" android:layout_height="fill_parent" android:text="@string/status_bar_latest_events_title" android:layout_alignParentLeft="true" />
<TextView android:textSize="@dimen/status_bar_expanded_notification_clear_button_text_size" android:textColor="@color/tw_status_bar_clear_btn_text" android:gravity="center" android:id="@id/clear_all_button" android:background="@drawable/tw_btn_default_small" android:padding="0.100000024dip" android:focusable="true" android:clickable="true" android:layout_width="@dimen/status_bar_expanded_clear_button_width" android:layout_height="fill_parent" android:layout_marginRight="4.0dip" android:text="@string/status_bar_clear_all_button" android:layout_alignParentRight="true" android:contentDescription="@string/accessibility_clear_all" />
</RelativeLayout>
</LinearLayout>
<com.android.systemui.statusbar.policy.NotificationRowLayout android:id="@id/notificationItems" android:layout_width="fill_parent" android:layout_height="wrap_content" systemui:rowHeight="@dimen/tw_notification_row_min_height" />
<com.android.systemui.statusbar.policy.NotificationRowLayout android:id="@id/latestItems" android:layout_width="fill_parent" android:layout_height="wrap_content" systemui:rowHeight="@dimen/tw_notification_row_min_height" />
</LinearLayout>
</ScrollView>
</FrameLayout>
<com.android.systemui.statusbar.phone.CloseDragHandle android:layout_gravity="bottom" android:orientation="vertical" android:id="@id/close" android:layout_width="fill_parent" android:layout_height="@dimen/tw_close_handle_height">
<RelativeLayout android:layout_width="fill_parent" android:layout_height="fill_parent">
<ImageView android:layout_gravity="bottom" android:layout_width="fill_parent" android:layout_height="@dimen/tw_close_handle_height" android:src="@drawable/tw_status_bar_close" android:scaleType="fitXY" />
<TextView android:textAppearance="@style/TextAppearance.StatusBar.Expanded.Network" android:gravity="center" android:layout_gravity="bottom" android:id="@id/carrier_label" android:layout_width="fill_parent" android:layout_height="@dimen/tw_close_handle_height" android:layout_marginBottom="10.0dip" />
</RelativeLayout>
</com.android.systemui.statusbar.phone.CloseDragHandle>
</FrameLayout>

Also, in the zipa re some transparent files that go in drawable-xhdpi.

Put them into that folder, then build/compile

EDIT:

Just noticed the above post... there's that tiny line sorted for you ;) That's the second edit.