Все отлично работает. Более того, если к примеру из справки добавить картинку, таким же способом, текст без проблем выводится поверх картинки:
CustomColor = EEAA99 ; Can be any RGB color (it will be made transparent below).
Gui +LastFound +AlwaysOnTop -Caption +ToolWindow ; +ToolWindow avoids a taskbar button and an alt-tab menu item.
Gui, Color, %CustomColor%
Gui, Font, s32 ; Set a large font size (32-point).
; Make all pixels of this color transparent and make the text itself translucent (150):
Gui, Add, Picture, x10 y25 w360 h55 +0x4000000, D:\temp\testing.bmp
Gui, Add, Text, x60 y25 vMyText cLime +BackgroundTrans, XXXXX YYYYY ; XX & YY serve to auto-size the window.
WinSet, TransColor, %CustomColor% 150
SetTimer, UpdateOSD, 200
Gosub, UpdateOSD ; Make the first update immediate rather than waiting for the timer.
Gui, Show, x0 y400 NoActivate ; NoActivate avoids deactivating the currently active window.
return
UpdateOSD:
MouseGetPos, MouseX, MouseY
GuiControl,, MyText, X%MouseX%, Y%MouseY%
return
Esc::
ExitApp