Here is the Montana law...
Hunter Orange Requirement – Any person hunting or accompanying hunters (including outfitters and guides) must wear a minimum of 400 square inches of hunter orange (fluorescent) material above the waist visible at all times.
The way I have seen the Montana Orange Rule interpreted is any form of orange, camo or solid, that is visible from ALL sides.
Wyoming is the same rule but they specify that orange camo patterns are ok.