That's pretty simple when I make art for ghosts I export them as transparent PNG I paint cyan only on their eyes then I import them to Godot and put ghost node layer over a player node (flashlight beam is in player node)
Thank you and Yes, you're right. I try to implement checking if the item in the room was taken it won't spawn again but I mess it up many times so I gIve up and changed from fixed item to spawn item randomly when you enter a room.