GUICtrlSetBkColor ?

Hi group

this is a test script i am trying to change the GUICtrlSetBkColor of  
$Graphic1 when a button is pushed  i went green an red
thanks for an help


#include <GUIConstants.au3>

#Region ### START Koda GUI section ### Form=
$Form1 = GUICreate("AForm1", 633, 447, 193, 115)
$Button1 = GUICtrlCreateButton("AButton1", 48, 168, 65, 33, 0)
$Button2 = GUICtrlCreateButton("AButton2", 184, 168, 73, 33, 0)
$Group1 = GUICtrlCreateGroup("", 296, 256, 41, 41)
$Graphic1 = GUICtrlCreateGraphic(312, 272, 17, 17)
GUICtrlSetBkColor(-1, 0xFF0000)
GUICtrlCreateGroup("", -99, -99, 1, 1)
GUISetState(@SW_SHOW)
#EndRegion ### END Koda GUI section ###

While 1
    $nMsg = GUIGetMsg()
    Switch $nMsg
        Case $GUI_EVENT_CLOSE
            Exit
       
        Case $Button1
$Graphic1 = GUICtrlCreateGraphic(312, 272, 17, 17)
GUICtrlSetBkColor(-1, 0xFF0000)
       
        Case $Button2
$Graphic1 = GUICtrlCreateGraphic(312, 272, 17, 17)
        GUICtrlSetBkColor(-1, 0x008000)
        Case $Graphic1
    EndSwitch
WEnd