Servis fridge freezer mo330al lights

Question

hi i have just purchased a second hand sevis mo330al fridge freezer.unfortunately it didnt come with a manual.on the top there are 3 lights a green then a red then a amber.when we first put it on they were all on then the red went off.could you tell me if the other 2 are suppose to be on constantly as there is a button under the amber one which can be switched off and on,so i am not sure if it should be off or on.i would be very grateful for some help. thanks maureen