Red line box (or solid filled circles) for very deep coins/treasure or artifacts of value.
Green in general is a color indicator, I use for various other targets mostly archaeological (old ruins or foundations but especially those non-metallic objects such as Indian flints, glass, pottery, carved stone with treasure signs).
White in general is a color indicator, I use for natural caves or man made tunnel entrances and mine shafts, other similar type excavations (including tombs).
Green line boxes in general for various other targets, mostly archaeological such as old ruins or foundations but especially non-metallic objects like flint arrowheads, bottles, pottery, and carved stone markers.
Red circles for places to check metal detecting, for mostly loose coins/treasure or artifacts of value, from surface down to 1-2 feet deep.